Chapter 3. Punctuation
3.1. A Functional Concept of Punctuation
Punctuation is placed in text to make meaning clear and to make
reading easier. The various punctuation marks perform four functions:
they (1) separate (a period separates sentences), (2) group or
enclose (parentheses enclose extraneous information), (3) connect (a
hyphen connects a unit modifier), and (4) impart meaning (a question
mark may make an otherwise declarative sentence interrogative). The
function of a punctuation mark is the basis for the rules governing
its use and should be the basis for determining whether or not it is
needed. The modern tendency is to punctuate to prevent misreading
(open style) rather than to use all punctuation that the grammatical
structure will allow (close style). Although the open style results
in a more inviting product, it does allow subjectivity, perhaps
arbitrariness, in the use of some marks, for example, the comma and
hyphen. Consistency in the author's or editor's subjective decisions
is vital to a well-punctuated report.
This chapter addresses the marks of punctuation, in alphabetical
order, presenting their functions, situations when the marks are
required or incorrect, and situations when the marks are appropriate
but optional. Because the exclamation point is so rare in technical
writing, it is not covered herein. Guidelines for its use parallel
those for the question mark (section 3.13).
3.2. Apostrophe
The functions of the apostrophe are to indicate possession; to
form the plurals of abbreviations, characters, and signs; and to
indicate omitted characters in contractions.
The rules for forming the possessive case of nouns are presented
in section possessive. An apostrophe is never used to form the
possessive of a personal pronoun.
We prefer to follow the GPO and to use the 's
to form the plural of symbols, abbreviations, acronyms, designations,
signs, numbers, and years:
x's
|
's
|
C-130's
|
PMT's
|
M.A.'s
|
4's
|
+'s
|
1970's
|
60's
|
Note: Chicago Manual of Style and WIT
recommend that the apostrophe be used in such plural constructions
only when necessary to avoid confusion.
47 Back to Top
An 's is used to form the plural of a word referred
to as the word itself, but the apostrophe is not necessary when the
word retains its meaning:
There can be no ands, ifs, and buts. (meaning no
conditions)
There can be no and's, if's, and but's. (meaning the
words cannot appear)
The apostrophe indicates letters left out of contractions,
for example, it's (it is), Gov't, and nat'l. Since contractions are
rare in formal writing, such use of the apostrophe is also rare.
3.3. Brackets
The nonmathematical function of brackets is to enclose editorial
insertions, corrections, and comments in quoted material and in
reference citations:
"These instruments [the radiometer and
scatterometer] have been used successfully aboard satellites
as well as aircraft."
Boeing Commercial Airplane Co.: Integrated Application of
Active Controls Technology. NASA CR-000000, [1977].
Although some authorities (Chicago Press 1982; Skillin et al.
1974; and Ebbitt and Ebbitt 1982) recommend brackets to enclose
material within parentheses, particularly in legal and scholarly
works, we have not found the nonmathematical use of parentheses
within parentheses to be misleading in Langley reports. Thus, we do
not recommend that brackets be used.
3.4. Colon
The function of the colon is to separate and introduce lists,
clauses, and quotations, along with several conventional uses.
Authorities disagree on usage of the colon and capitalization after a
colon. The following guidelines generally correspond to Words Into
Type (Skillin et al. 1974).
3.4.1. Colons That Introduce
A colon has the same separating force as a period. It thus brings
a sentence almost to a halt (Bernstein 1981).
Because of its strong separating function, an introductory
colon should generally be used only after a complete sentence. In
particular, do not use a colon between a verb or preposition and its
direct object:
Wrong
|
The components of the rack-mounted electronics are: power
supplies, the gimbal controller, . . .
|
Correct
|
The components of the rack-mounted electronics are power
supplies, the gimbal controller, . . .
|
Wrong
|
The scatterometer is separated into: a gimbal, a
transmitter-receiver assembly, and rack-mounted
electronics.
|
Correct
|
The scatterometer is separated into a gimbal, a
transmitter-receiver assembly, and rack-mounted
electronics.
|
48 Back to Top
Nor should a colon be used after such introductory phases as
that is, for example, and such as (the colon replaces
them):
Wrong
|
Microwave instruments are used for remote sensing of
environmental variables such as: sea ice, soil moisture, and
surface wind speed.
|
Either
|
Microwave instruments are used for remote sensing of
environmental variables, such as sea ice, soil moisture, and
surface wind speed.
|
Or
|
Microwave instruments are used for remote sensing of
environmental variables: sea ice, soil moisture, and surface
wind speed.
|
When items of a list are numbered, the numbers do not
affect the punctuation:
The quantities calculated from microwave instruments are
(1) radiometer wind speed, (2) radiometer rain rate, and (3)
scatterometer wind vector.
Remember that the colon has strong separating force; do not use it
where separation is not grammatically desirable.
When using a colon incorrectly, an author probably wants to
emphasize the material that follows. The editor should consider a
correction that preserves this emphasis, for example, itemization
(see section 2.6) or correct use of the colon.
Lists
A colon is an elegant way of introducing a list and at the same
time emphasizing the elements of the list (by separating them from
the rest of the sentence). Such lists might consist of words, phrases
(prepositional, infinitive, or noun), or even clauses.
Use a colon to introduce a list in apposition to a
noun:
The scatterometer is separated into three assemblies: a
gimbal, a transmitter-receiver assembly, and rack-mounted
electronics.
Use a colon to introduce a list whose introductory
statement contains the words as follows or the
following:
The rack-mounted electronics consist of the following:
power supplies, the gimbal controller, . . .
Use a colon to introduce a list that amplifies an
introductory sentence:
The purpose of this report is twofold: to evaluate the
performance of the instruments and to expand the data base.
49 Back to Top
One very effective way to emphasize a list, and at the same time
make a long list easy to read, is to number and display the list:
The scatterometer is separated into three assemblies:
- A gimbal
- A transmitter-receiver assembly
- Rack-mounted electronics
When the introduction to a displayed list is not a complete
sentence (the items of the list complete it), no colon is used
(Chicago Press 1982; and Skillin et al. 1974):
The purposes of this report are
- To evaluate the performance of the instruments
- To expand the data base
There is a trend toward using a colon after a verb preceding a
displayed list (are in the above example). Such use of the
colon is grammatically suspect and unnecessary.
Clauses
A colon may be used between two clauses when the second amplifies
or restates the first, for example,
The toughness of pseudo-maraging steel degrades at
cryogenic temperatures: at -320 deg F, its Charpy impact energy is
6 ft-lb.
Note: The first word after a colon may be capital only
when the capital begins a complete sentence; however,
capitalization of a complete sentence after a colon is
optional.
The dash (section 3.6.2) and semicolon (section 3.15.1) may also
be used in this situation. The colon is more formal than the dash and
has more introductory force than the semicolon.
A colon is particularly useful for introducing displayed equations
(which can be considered clauses), particularly when the equation
symbolically restates the preceding sentence:
The out-of-plane deflection wo can be
approximated by a truncated kinematically admissable series:
wow2k-1
cos [(2k -1)]
50 Back to Top
Quotations
A colon may be used to introduce a direct quotation, particularly
if the quote is long (more than one sentence) or not built closely
into the sentence (Ebbitt and Ebbitt 1982):
In reference 6, he states this conclusion: "Thermal
neutron fluxes up to 1020 might be required."
However, a comma is usually sufficient for direct quotations
(section 3.5.1):
In reference 6, he states, "Thermal neutron fluxes up to
1020 might be required."
Neither a colon nor a comma should be used before an indirect
quotation:
In reference 6, he concludes that thermal neutron fluxes
up to 1020 might be required.
3.4.2. Conventional Uses of the Colon
The colon is used by convention as follows:
- After the salutation in formal letters: Dear Sir:
- Between hours and minutes in time: 11:30 a.m.
- In reference citations: Slater, Philip N.: Remote Sensing .
. .
- To express ratios: 2:1 mixture
3.4.3. Use With Other Marks
A colon follows closing parentheses and closing quotation
marks.
3.5. Comma
Of all the marks of punctuation, the comma requires the most
judgment. To punctuate with commas requires not only compliance with
a set of rules but also thorough understanding of the material being
punctuated. Commas can change meaning!
The primary functions of the comma are to separate and to enclose
elements of a sentence. The function of a particular comma is
important: when it separates, it stands alone, but when it encloses,
it needs a partner. The instances when commas separate sentence
elements are discussed first in this section, and then the instances
when commas enclose.
3.5.1. Commas That Separate
Many separating uses of the comma are optional in an open style.
If commas are used whenever possible, they chop up the text and can
even render it difficult to read, contrary to the purpose of
punctuation.
51 Back to Top
Independent clauses
Independent clauses joined by coordinate conjunctions (see section
1.8.1) may be separated by a comma:
The mixing noise dominates the spectrum, but the
background noise peaks at a high frequency.
When the independent clauses are short and closely related,
the comma may be omitted:
Each performance of an experiment is called a trial and
its result is called an outcome.
The comma is usually retained between clauses joined by the
coordinate conjunctions but and for, in order to
emphasize the contrast.
When the independent clauses are complicated and contain
internal commas, a semicolon may be used to separate them.
Do not use a comma to separate independent clauses without
a coordinate conjunction:
Wrong
|
The differences were generally about 11 percent, however,
larger differences occurred at
= 15 °.
|
Either
|
The differences were generally about 11 percent, but
larger differences occurred at
= 15 °.
|
Or
|
The differences were generally about 11 percent; however,
larger differences occurred at
= 15 °.
|
Do not separate compound predicates with a comma unless
they are long and require a comma for clarity.
Poor
|
Viewing through the atmosphere increases the apparent
reflectance for low-reflectance objects (e.g., p =
0.1), and decreases the apparent reflectance for
high-reflectance objects (e.g., p = 0.7).
|
Correct
|
Viewing through the atmosphere increases the apparent
reflectance for low-reflectance objects (e.g., p =
0.1) and decreases the apparent reflectance for
high-reflectance objects (e.g., p = 0.7).
|
When compound predicates are so long that a comma seems
appropriate, they are perhaps too long. A comma to separate them may
not sufficiently clarify them.
52 Back to Top
Elements of series
Commas (at least) are required to separate series of three or more
elements:
The flight navigation system also provides altitude,
roll, pitch, yaw, and ground speed.
Pressures at the bulkhead, in the cove, and at the seal were
measured.
Wind speed is obtained from antenna brightness temperature,
rain rate is obtained from the brightness temperature difference
at two frequencies, and wind vector is obtained from radar cross
section.
We prefer a comma before the conjunction in a series. This serial
comma is often necessary to prevent misreading.
Introductory phrases and
clauses
A comma may be used to separate an introductory phrase or clause
from the main clause:
If the variable t is actually time, then a
is frequency.
As discussed in reference 4, one has considerable freedom in
defining the Fourier transform pair.
It is standard practice to put the comma after all introductory
clauses and all introductory phrases containing a verb form (Ebbitt
and Ebbitt 1982):
Clause
|
Although some mathematicians are not comfortable with
this intuitive definition, it is widely used.
|
Participal phrase
|
Called mean square calculus, this theory is based on the
concept of mean square convergence.
|
Gerund phrase
|
In analyzing the experiment, we try to statistically
describe the whole random process.
|
Infinitive phrase
|
To understand this concept, note that periodic functions
may be expanded in Fourier series.
|
The comma is optional after a short introductory adverbial phrase
unless the comma is required for clarity:
Either
|
In recent years, the delta function has been rigorously
defined.
|
Or
|
In recent years the delta function has been rigorously
defined.
|
53 Back to Top
Wrong
|
Soon after the photon density becomes steady as gains and
losses balance each other.
|
Better
|
Soon after, the photon density becomes steady as gains
and losses balance each other.
|
Do not place a comma after an introductory phrase that
immediately precedes the verb it modifies:
Wrong
|
Only in recent years, has the delta function been
rigorously defined.
|
Correct
|
Only in recent years has the delta function been
rigorously defined.
|
Remember that after introductory clauses and phrases the comma is
separating, not enclosing. A comma is appropriate after an internal
phrase or clause, but it is not appropriate before unless the phrase
or clause is nonrestrictive (see section commasenclose).
A comma follows, but does not precede, restrictive
introductory elements:
Wrong
|
Recombination rate is larger than quenching rate, and,
after lasing is achieved, both are smaller than
photo-break dissociation rate.
|
Correct
|
Recombination rate is larger than quenching rate, and
after lasing is achieved, both are smaller than
photo-break dissociation rate.
|
Wrong
|
The laser pulse was reasonably stationary, although,
at 1.6 msec, motion of the arc is evident.
|
Correct
|
The laser pulse was reasonably stationary, although at
1.6 msec,motion of the arc is evident.
|
A comma both precedes and follows nonrestrictive
introductory elements:
Correct
|
Note that, even though they are unbounded, the
delta functions are plotted as arrows with their heights
representing the coefficient magnitudes.
|
Coordinate adjectives
"Adjectives are coordinate if (1) they can be linked by
and and (2) they independently modify the substantive" (Linton
1962).
Separate by commas only those consecutive adjectives that
are coordinate. Deciding whether adjectives are coordinate can be
tricky; two tests might help. First try inserting and
between the adjectives:
The delta function has a long controversial history.
(long and controversial?)
54 Back to Top
A comma is appropriate between long and
controversial.
Consider a linear shift-invariant system.
(linear and shift-invariant?)
If still in doubt, try reversing the adjectives (if they
independently modify the noun, order makes no difference):
Consider a shift-invariant linear system.
The adjectives shift-invariant and linear are
probably coordinate, but the final decision requires someone who
understands the technical meaning of the adjectives. (Good luck with
trying to explain this grammatical dilemma!)
When in doubt, do not insert the comma between adjectives. The
current tendency is to omit the comma between two coordinate
adjectives anyway (Ebbitt and Ebbitt 1982). The comma adds emphasis
though to the adjectives as separate modifiers.
Elliptical constructions
When clauses in a sentence contain repeated elements (for example,
the verb), the omission of these elements is indicated by a
comma:
Wind speed is obtained from antenna brightness
temperature; rain rate, from the brightness temperature difference
at two frequencies; and wind vector, from radar cross section.
The comma may be omitted if the clauses are short:
Wind speed is obtained from antenna brightness
temperature, and wind vector from radar cross section.
Note: See section 3.15.4 for the use of the semicolon in
elliptical constructions.
Direct quotations and questions
Direct quotations and questions are separated from the rest of the
sentence with either commas or colons. A colon is used to introduce a
long or formal quotation.
Separate a direct quotation or question from the rest of
the sentence with a comma:
In reference 6, he states, "Thermal neutron fluxes up to
1020 might be required."
The obvious question is, how good is this estimate?
Note: The first word of the question may or may not be
capitalized.
55 Back to Top
Neither a comma nor a colon sets off an indirect quotation
or one that is part of the grammatical structure of the sentence:
In reference 6, he stated that thermal neutron fluxes up
to 1020 may be required.
In case of fire, the command for stopping the test is "Recover,
fire."
3.5.2. Commas That Enclose
A comma that encloses requires a partner, which may be another
comma or a colon, semicolon, period, question mark, or exclamation
mark.
Nonrestrictive modifiers
A nonrestrictive modifier does not affect the meaning of the basic
sentence; it could be removed from the sentence without altering
meaning.
Nonrestrictive modifiers must be enclosed by commas (at
least). The important point to remember is that an enclosing comma
requires a partner, which can be another comma or another mark of
punctuation.
The nonrestrictive prepositional and verbal phrases are enclosed
with commas in the following examples:
The record need not be continuous but may, in
fact, be digital data.
Theoreticians prefer to work in terms of radian frequency,
defined for both positive and negative frequencies.
The power spectral density is integrated over some finite
bandwidth, such as a one-third octave.
The second integral, being the integral of an odd function
over even limits,is zero.
Be sure to distinguish between restrictive and
nonrestrictive internal phrases that introduce clauses (see section
introductory):
Restrictive
|
A random process is stationary if for all n, its
nth density function is independent of time.
|
Nonrestrictive
|
The coefficient could be placed elsewhere because,
though preferred, the placement shown is
arbitrary.
|
Nonrestrictive relative clauses are enclosed with
commas:
Restrictive
|
The most common panel methods are the codes which Hess
and Smith (ref. 26) designed for nonlifting bodies.
|
Nonrestrictive
|
The most common panel methods are the codes of Hess and
Smith (ref. 26), which were developed for nonlifting
bodies.
|
56 Back to Top
Nonrestrictive adverbial clauses are enclosed with
commas:
Restrictive
|
The last chapter introduces specialized areas where
research is in progress.
|
Nonrestrictive
|
The power spectral density of the signal is shown in
figure 9, where arrows represent delta functions.
|
Restrictive
|
Two random processes are uncorrelated if their cross
correlation satisfies equation (6).
|
Nonrestrictive
|
Independent random processes are uncorrelated, since
their cross correlation always satisfies equation
(6).
|
Whether restrictive or nonrestrictive, an introductory
adverbial clause is separated by a comma from the clause it modifies
(see section introductory).
When an internal adverbial clause precedes the clause that
it modifies, do not place a comma before it unless it is clearly
nonrestrictive:
Wrong
|
Recombination rate is larger than quenching rate, and,
after lasing is achieved, both are smaller than
photo-break dissociation rate.
|
Correct
|
Recombination rate is larger than quenching rate, and
after lasing is achieved, both are smaller than
photo-break dissociation rate.
|
The following guidelines, taken from Rowland, might be helpful in
determining whether the clause is restrictive or nonrestrictive.
Adverbial clauses can be categorized as follows:
- Time clauses-introduced by when, whenever, after, as soon
as, just as, before, since, until, while-are restrictive when
they modify the main verb.
- Place clauses-introduced by after, before, where,
wherever-are usually restrictive, but may be
nonrestrictive.
- Manner clauses-introduced by how, just as, as, as if, as
though-are usually restrictive.
- Comparison or degree clauses-introduced by else, other,
rather, as, than-are usually restrictive.
- Condition clauses-introduced by if, as though, except,
provided, unless, whether-are usually restrictive.
- Concession clauses-introduced by although, even, while,
whereas, though-are always nonrestrictive.
- Cause or reason clauses introduced by because are
usually restrictive, but those introduced by since, as,
inasmuch as are usually nonrestrictive.
- Purpose clauses-introduced by so that, in order
that-are restrictive.
- Result clauses-introduced by so that-are
nonrestrictive.
57 Back to Top
Appositives
Words or phrases in apposition are enclosed by commas unless the
appositive is restrictive. A restrictive appositive is required to
distinguish its antecedent from other members of the same class:
Restrictive
|
The noble gas argon was chosen for the lasant
gas.
|
Nonrestrictive
|
Argon, the lightest noble gas that will lase, was
chosen for the lasant gas.
|
Dashes (em) may enclose appositives to improve clarity,
particularly when the appositive contains commas (section
dashenclose).
The word or often precedes nonrestrictive
appositives. The appositional or always requires
enclosure:
The concept of a laser powered directly by nuclear
energy, or a direct nuclear-pumped laser, came into existence
shortly after discovery of the laser.
Commas are usually omitted around symbolic appositives,
whether restrictive or not:
Restrictive
|
The coefficients CL and Cm
are plotted in figure 23.
|
Nonrestrictive
|
The lift coefficient CL is plotted in
figure 23.
|
However, if the author or editor prefers, nonrestrictive symbolic
appositives may be enclosed by commas:
The two most sensitive parameters in the estimations,
and
are compared with measured values in table II.
Interrupting elements
Parenthetical phrases, rhetorical adverbs, antithetical phrases,
introductory words, and other interruptive sentence elements may be
enclosed by commas when they are nonrestrictive:
Parenthetical phrase
Auxiliary meteorological data used herein, such as
vorticity, have been computed from NMC isobaric height fields.
Rhetorical adverb
The time between independent measurements cannot be
reliably estimated; it can be assumed, however, to lie
between 20 and 120 minutes.
Note: The placement and punctuation of rhetorical
adverbs affect emphasis (see section 2.6).
58 Back to Top
Antithetical elements
In winter, clouds near the tropopause are associated with
negative vorticity, not with positive vorticity as most
meteorologists are accustomed to believing.
Interruptive words or phrases
For 33-mm-diameter particles, for example,
partial loss of laminar flow is predicted for large number
densities.
Phrases with common termination
Enclose by commas a phrase with termination that also reads back
to a previous phrase:
An aircraft flying through clouds will lose a significant
portion, if not all, of its laminar flow.
The particle-concentration data have nearly the same
latitudinal, but a significantly different seasonal,
distribution from that of the cloud-encounter data.
Nominative absolute
A nominative absolute phrase (that is, a noun with no grammatical
function in the sentence modified by a participle) is nonrestrictive
and thus is enclosed by commas:
Most confidence may be placed in the statistics for the
30 deg N to 60 deg N latitude band, more data having been
taken at these latitudes.
3.5.3. Conventional Uses of the Comma
The following conventional uses of the comma should be considered
enclosure rather than separation:
Dates
|
The study was conducted from January 15, 1975, to
February 1, 1979, aboard commercial airliners.
|
But
|
The study was conducted from January 1975 to February
1979 aboard commercial airliners.
|
Geographical names and addresses
These instruments were carried on commercial airliners en
route from Chicago, Illinois, to London, England.
The computer program is available from COSMIC, 112 Barrow Hall,
University of Georgia, Athens, GA 30602.
59 Back to Top
Specifying phrases
This conclusion was drawn from data in Volume II, page
157, of reference 16.
Degrees, titles, affiliations, etc.
Members of the committee consisted of J. J. Deluisi,
Ph.D., NOAA Environmental Research Laboratory; J. P. Friend III,
Drexel University; and M. P. McCormick, chairman, NASA Langley
Research Center.
Names
Refer to the report by J. J. Deluisi, Jr., and James P.
Friend III:
Deluisi, J. J., Jr.; and Friend, James P., III:
Listing of Multi-Spectral dots
The comma is used by convention to separate thousands in numbers
of five or more digits; but in technical work, we prefer a (thin)
space over a comma because in some foreign languages the comma
indicates the decimal point:
Numbers
Correct
|
There were 88,000 data points, 2500 of which had to be
discarded.
|
Preferred
|
There were 88 000 data points, 2500 of which had to be
discarded.
|
3.5.4. Use With Other Marks
Commas are used with other marks of punctuation as follows:
Commas precede closing quotation marks.
Commas follow a closing parenthesis if the comma would
appear without the parenthetical matter.
Commas rarely precede an open parenthesis, only if the
parenthetical matter clearly limits the following word (see section
3.10).
Other marks of punctuation--semicolon, colon, dash,
period--supercede and replace the comma; thus, the "partner" of an
enclosing comma may be another mark of punctuation.
3.6. Em Dash
Like the comma, the em dash2 is used both to enclose
and to separate, and like the comma, an enclosing dash needs a
partner. In fact, enclosing dashes
2In typeset material, there are two dashes: the em dash,
which is the width of the letter M, and the en dash, which is
half as wide. In typewritten material, the em dash is represented by
two hyphens with no space around them, and an en dash is represented
by a hyphen. Here the em dash will be referred to as simply
"dash."
60 Back to Top
are replacements for enclosing commas in order to add emphasis.
Ebbitt and Ebbitt (1982) suggest a useful philosophy toward using the
dash:
If used sparingly, the dash suggests a definite tone, often a note
of surprise or an emphasis equivalent to a mild exclamation. If used
regularly in place of commas, colons, and semicolons, it loses all
its distinctiveness and becomes a sloppy substitute for conventional
punctuation. At its best the dash is a lively, emphatic mark.
3.6.1. Dashes That Enclose
Dashes may replace commas in enclosing interrupting elements and
non-restrictive modifiers and appositives (see section 3.5.2).
Dashes are appropriate when a comma might be misread, for
example, as a serial comma:
Wrong
|
The lasant gas, argon, and He were allowed to mix for 45
minutes.
|
Better
|
The lasant gas--argon--and He were allowed to mix for 45
minutes.
|
Dashes are also appropriate when the enclosed element
contains internal commas:
Of the lasant gases studied-argon, xenon, krypton, and
neon-argon offers the most promise.
The most promising lasant gas-argon, which is the lightest gas
studied-produced laser output power of 4 W.
Use dashes when the enclosed element needs emphasis.
Enclose by dashes a complete sentence that interrupts
another:
Wrong
|
The one-sided spectrum, engineers call it simply
"spectrum," is the output of most spectral analyzers.
|
Correct
|
The one-sided spectrum-engineers call it simply
"spectrum"-is the output of most spectral analyzers.
|
Commas are insufficient to enclose an interrupting sentence;
dashes or parentheses are required.
The choice of commas, dashes, or parentheses to enclose a
nonrestrictive or interrupting element depends on the relation of the
element to the rest of the sentence and on the emphasis it requires
( Effective Revenue Writing 1, IRS 1962):
Commas (most frequently used) indicate only a slight
separation in thought from the rest of the sentence.
Dashes emphasize the element enclosed and clarify meaning
when the element contains internal commas.
Parentheses indicate that the enclosed element is only
loosely connected to the rest of the sentence and therefore tend to
de-emphasize it.
61 Back to Top
3.6.2. Dashes That Separate
The dash is used to separate sentence elements in essentially
three situations:
A dash separates a group of antecedents from their pronoun
that is the subject of the sentence:
Argon, xenon, krypton, and neon--these are the possible
choices of noble gases for use in nuclear pumped lasers.
In a displayed list, a dash may separate the item from an
explanatory statement:
Support systems for the facility supply the following:
- Air--The 600-psi system can deliver a flow rate of 300
lb/sec for 3 min.
- Cooling water--The closed-loop system delivers 450 gal/min
at 550 psig.
- Gaseous propellants--Hydrogen, oxygen, and nitrogen are
supplied from tanks at 2400 psia.
A dash may separate two clauses when the second amplifies
or restates the first:
The toughness of pseudo-maraging steel degrades at
cryogenic temperatures--at -320 deg F, its Charpy impact energy is
6 ft-lb.
The colon (section 3.4.1) or semicolon (3.15.1)may also be used
for this purpose. The dash is less formal than the colon and more
emphatic than the semicolon.
A dash may precede a phrase like that is, namely,
and for example when it introduces a summarizing or
explanatory phrase or clause at the end of a sentence, but a comma or
semicolon may also be used (Rowland 1962). If an explanatory clause
follows the sentence, a semicolon is necessary; if an explanatory
phrase follows, a comma is sufficient. If the explanatory phrase or
clause receives enough emphasis by being at the end of the sentence,
use a comma or semicolon, whichever is appropriate:
Moderate emphasis
|
Other random processes have average properties that vary
appreciably with time, for example, the load demand on an
electric power generating system.
|
|
Some random processes are reasonably independent of the
precise time; that is, measurements made at different times
are similar in their average properties.
|
A dash would further emphasize the explanatory material:
Emphatic
|
Other random processes have average properties that vary
appreciably with time--for example, the load demand on an
electric power generating system.
|
62 Back to Top
|
Some random processes are reasonably independent of the
precise time-that is, measurements made at different times
are similar in their average properties.
|
3.6.3. Conventional Uses of the Dash
The dash is used by convention as follows:
To separate a title and subtitle
Large Space Systems Technology --1984
Energy Efficient Transport Technology --Program Summary and
Bibliography
In vague or open-ended dates
3.6.4. Use With Other Marks
A semicolon, colon, question mark, period, or exclamation point
--but not a comma-- supercede and replace a dash; that is, a
semicolon, colon, or period may be the "partner" of an enclosing
dash.
3.7. En Dash
The uses of the en dash3 are conventional:
The en dash indicates inclusive or continuing numbers or
dates:
pp. 233--235
|
or
|
Oct. 1975--Jan. 1976
|
The en dash is not appropriate in a from . . . to . . . or
a between . . . and . . . construction:
Wrong
|
between 1975--1978
|
Wrong
|
from 1975--1978
|
The en dash connects a unit modifier with a two-word or
hyphenated element:
New York--London flight
shock-wave--boundary-layer interaction
See section 3.16 for discussion of the slash (/) used in place of
an en dash.
The en dash is used in place of a hyphen in all capital
text.
3 An en dash (which is half the width of an em dash) is
available in typeset material. In typewritten material, a hyphen is
used in place of an en dash.
63 Back to Top
3.8. Hyphen
The hyphen4 is used to connect words or parts of words:
it connects the syllables of words broken at the ends of lines, it
connects prefixes and suffixes to words, and it connects compound
words. The modern trend is away from hyphenation. Permanent compounds
tend to become solid, and temporary compounds tend to be hyphenated
only when necessary to avoid ambiguity.
3.8.1. Word Division
Words may be hyphenated at the ends of lines between syllables.
Proper places to break words are determined from your favorite
dictionary. We prefer
Webster's Third New International Dictionary of the English
Language, Unabridged. G.& C. Merriam Co., c.1967.
Webster's Ninth New Collegiate Dictionary. Merriam-Webster,
Inc., c.1983.
In general, end-of-line hyphens should be avoided when possible.
To avoid extremely ragged right margins in unjustified text or to
avoid large spaces between words in justified text, words may be
hyphenated at the ends of lines. The following guidelines for
end-of-line hyphenation are taken from The Chicago Manual of Style
(Chicago Press 1982):
Words may be divided only between syllables. Consult a
dictionary for syllabification.
Divisions leaving one letter at the end or beginning of a
line are not permissible.
Two-letter syllables may be left at the end of a line, but
two-letter endings may not be carried to the next line.
The last word of a paragraph, page, or similar item (e.g.,
reference citation, figure caption) should not be divided.
A hyphenated compound should be divided only at the hyphen.
Likewise it is best to divide solid compounds at the natural breaks
(after-body), after prefixes (dis-comfort), and before suffixes
(other-wise).
Avoid, if possible, several consecutive end-of-line
hyphens.
3.8.2. Prefixes
Hyphens are sometimes used to connect a prefix to a word. The
tendency is to eliminate the hyphen after a prefix.
Hyphens are always required with the following
prefixes:
all-
|
quasi-
|
half-
|
self-
|
quarter-
|
ex-
|
4 In typewritten material, the hyphen represents an en
dash, and two hyphens with no space around them are preferred for
representing an em dash.
64 Back to Top
Use a hyphen to attach a prefix to a proper noun or
adjective:
un-American
anti-Arab
Hyphenate a homograph (a word with two meanings) that might
be misunderstood without the hyphen:
unionized
|
un-ionized
|
recover
|
re-cover
|
coop
|
co-op
|
multiply
|
multi-ply
|
Hyphenate a word that might be misread or difficult to read
without the hyphen:
un-uniform
post-stall
sub-subcommittee
When a vowel would be doubled or a consonant tripled, use
the hyphen:
micro-organism
anti-inflation
Note: The prefixes co, de, pre, pro, and
re are printed solid even if a vowel will be doubled:
cooperation
preexist
Use a hyphen to attach a prefix to a hyphenated compound
word:
non-civil-service position
pseudo-steady-state system
3.8.3. Suffixes
Hyphens are rarely used to connect a suffix to a word.
Use the hyphen to avoid tripling a consonant:
shell-like
hull-less
Use the hyphen when the suffix like is attached to a
proper noun.
3.8.4. Compound Words
Compound words may be (1) permanent, their form (solid or
hyphenated) being determined by usage and often appearing in
dictionaries, or (2)temporary, being hyphenated. Most permanent
compounds tend to become solid (without hyphen) with usage, and most
authorities (Bernstein 1981; G.P.O. 1984; and Skillin et al. 1974)
prefer to avoid forming temporary compounds. Thus, the trend is away
from hyphenation.
65 Back to Top
Compound nouns
Most permanent prepositional-phrase compound nouns are hyphenated,
and most other permanent compound nouns are solid:
right-of-way
|
workbench
|
mother-in-law
|
cupboard
|
Some noun phrases are in the process of becoming permanent
compounds; but although they are defined in the dictionary, they are
not yet hyphenated. For example, Webster's Ninth New Collegiate
Dictionary lists
|
|
right-of-way, n. & adj.
|
But
|
|
state of the art, n.; state-of-the-art, adj.
|
The dictionary is the best source for hyphenation and spelling of
permanent compound nouns.
Formation of a temporary compound noun with a hyphen is
appropriate when a combination of several nouns is one entity:
wing-body
writer-editor
Compound verbs
Hyphenate an active compound verb derived from a noun form
consisting of separate words:
Langley flight-tested that configuration.
To cross-brace such a structure is impossible.
But the passive verb form need not be hyphenated:
That configuration was flight tested.
Such a structure could not be cross braced.
Unit modifiers
Most authorities (for example, Bernstein 1981 and G.P.O. 1984)
advocate hyphenating unit modifiers only when necessary to avoid
ambiguity. See section 1.5.2; the guidelines for hyphenation are
repeated here:
A unit modifier should not be hyphenated
66 Back to Top
- When the first element of the unit modifier is a comparative
or superlative: higher order calculations
- When the first element is an adverb ending in ly:
relatively accurate prediction
- When the unit modifier is a foreign phrase: a priori
condition
- When the unit modifier is a proper name: North Carolina
coast (but Anglo-American plan)
- When the unit modifier has a letter or number designation as
its second element: material 3 properties
- When the unit modifier is enclosed in quotation marks:
``elliptical style'' symbol list
- When the unit modifier is a scientific name of a chemical, an
animal, or a plant which is not normally hyphenated: nitric
oxide formation
A unit modifier should always be
hyphenated
- When the unit modifier contains a past or present participle:
flight-tested model, decay-producing moment
- When the unit modifier is a combination of color terms:
blue-gray residue
- When a connecting word is implied in the unit modifier:
lift-drag ratio, Newton-Raphson iteration
- When the unit modifier contains numbers (other than number
designations): three-degree-of-freedom simulator,
0.3-metertunnel
3.9. Italics
Why is a section on italics appearing in a chapter on punctuation?
The purpose of italics very closely resembles the purpose of
punctuation, to make meaning clear and reading easier. According to
Words Into Type (Skillin et al. 1974), "Italics are used to
distinguish letters, words, or phrases from the rest of the sentence
so that the writer's thought or the meaning and use of the italicized
words will be quickly understood." Italics are used to distinguish
elements to be emphasized, special terminology, symbols, and words or
letters to be differentiated from text. In addition, there are
several conventional uses for italics.
In typewritten text, underscore replaces italics and should be
used only when absolutely necessary. In many instances, underscore is
not used in typewritten text when italics would be appropriate in
typeset text.
3.9.1. Italics for Emphasis
Words may be italicized when they would be stressed if spoken
(Ebbitt and Ebbitt 1982). Italics are especially appropriate if the
emphasis would be lost when written:
Of all the events affecting Langley history, only two
have caused major trauma. The second was the Sputnik
crisis.
67 Back to Top
Only rarely would a whole sentence be italicized for emphasis and
never a whole passage (Chicago Press 1982). As a matter of fact,
overuse of italics causes them to lose their force. Italics for
special effects "are used less and less ..., especially by mature
writers who prefer to obtain their effect structurally ... writers
who find themselves underlining frequently for emphasis might
consider (1) whether many of the italics are not superfluous, the
emphasis being apparent from the context, or (2) if the emphasis is
not apparent, whether it cannot be achieved more gracefully by
recasting the sentence" (Chicago Press 1982). Consider the following
sentences:
Although holographic interferometry and modulation
transfer function techniques were applied, a simple
shadowgraph system eventually identified the
flow-visualization problem.
- The flow-visualization problem was eventually identified not
by holographic interferometry, not by modulation transfer function
techniques, but by a simple shadowgraph system.
3.9.2. Italics for Special Terminology
A key term in a discussion or a technical term accompanied by its
definition is often italicized on first use:
Caustics, concentrations of light corresponding to
a family of rays, manifest themselves as bright streaks on the
photographs.
For coined terms or technical terms used in a nonstandard way,
quotes are preferred to italics (see section 3.14.2).
3.9.3. Italics for Differentiation
Italicize a word used not to represent an idea as usual, but as
the word itself:
A colon is not used after that is, for example,
or such as.
Likewise, letters used as letters are italicized:
The operator presses the letter n to indicate
"no" and the letter y to indicate "yes."
Letters indicating shape (V-tail, L-shaped), letter designations
(case A, appendix C), and letters indicating subdivisions (figure
1(a), equation (2c)) are not italic. Sans serif letters may be used
to indicate shape, but roman type is also acceptable.
Note that the plurals of italic words used as words and italic
letters used as letters are formed with roman s's:
and's, if's, and but's
i's and o's
68 Back to Top
3.9.4. Italics for Symbology
Most mathematical symbols and letter symbols representing a
physical concept are italic, whether within roman or italic text.
Chemical symbols, computer symbols, and abbreviations are not italic.
Symbols representing vectors, tensors, and matrices may be set in
boldface roman type if available.
In typewritten text, we recommend double spacing around symbols to
distinguish those that would normally be italic.
3.9.5. Conventional Uses for Italics
There are several items that are italicized by convention:
Titles and subtitles of books, reports,5
compilations, newspapers, and periodicals are italicized, but not
titles of articles, meeting papers, theses, papers in compilations,
or patents:
Slater, Philip N. 1980: Remote Sensing---Optics and
Optical Systems. Addison-Wesley Publ. Co., Inc.
Elterman, L. 1970: Vertical-Attenuation Model With Eight
Surface Meteorological Ranges 2 to 14 Kilometers.
AFCRL-70-0200, U.S. Air Force, Mar. (Available from DTIC as AD 707
488.)
Bowker, D. E.; Davis, R. E.; Von Ofenheim, W. H. C.; and
Myrick, D.~L. 1983: Estimation of Spectral Reflectance Signatures
From Spectral Radiance Profiles. Proceedings of the
Seventeenth International Symposium on Remote Sensing of
Environment, Volume II, Environmental Research Inst. of
Michigan, pp. 795--814.
Allen, William A.; and Richardson, Arthur J. 1968: Interaction
of Light With a Plant Canopy. J. Opt. Soc. America, vol.
58, no. 8, Aug., pp. 1923--1928.
Weidner, Elizabeth H.; and Drummond, J. Philip 1981: A
Parametric Study of Staged Fuel Injector Configurations for
Scramjet Applications. AIAA-81-1468, July.
Nemeth, Michael Paul 1983: Buckling Behavior of Orthotropic
Composite Plates With Centrally Located Cutouts. Ph.D. Diss.,
Virginia Polytechnic Inst. & State Univ., May.
Foreign words that will be unfamiliar to readers are
italicized, but not foreign proper names (Challais-Meudon,
Gottingen), foreign currency (lira, franc), foreign titles of
documents, or foreign phrases that have been adopted into English.
(See list of foreign words and phrases, Words Into Type).
Biological names of genera, species, and varieties are
italicized, but not higher classifications. Refer to CBE (1978) for
more complete information.
5 Most authorities on style do not indicate whether or not
to italicize report titles; Tichy and Fourdrinier (1988) recommend
italics for titles of long reports. We prefer italic report
titles.
69 Back to Top
The name of a specific aircraft, spacecraft, ship, or train is
italicized, but not the name or designation of a class of craft or
the abbreviations S.S. or H.M.S.:
S.S. United States
|
but
|
DC-3
|
Space Shuttle Columbia
|
|
F-14 Tomcat
|
Apollo 12
|
|
Project Apollo
|
3.9.6. Italics With Typefaces Other Than
Roman
The rules and guidelines discussed so far in this section are
based on the assumption that the surrounding text is roman. If the
surrounding text is not roman, adjustments must be made:
The typeface used for symbols remains italic even when the
surrounding typeface changes.
Items other than symbols that are normally set in italic on
roman type are set in roman on italic type.
Items other than symbols that are normally set in italic on
roman type may be quoted in caps and small caps or boldface type.
3.9.7. Italics With Punctuation
The standard printer's rule is to set punctuation marks in the
typeface of the letter preceding them (Chicago Press 1982). This rule
does not apply to parentheses and brackets however. Also Skillin et
al. (1974) prefer that quotation marks, question marks, and
exclamation marks, as well as parentheses, be set according to the
context of the sentence.
3.10. Parentheses
Parentheses may be used to enclose nonrestrictive or interrupting
elements. Commas or dashes may also be used for this purpose (see
section 3.6.1).
Parentheses are most appropriate to enclose a
nonrestrictive element that is only loosely connected to the sentence
and could be left out without damaging the sentence.
Do not insert a parenthetical element with no relation
whatever to the rest of the sentence. The following example is taken
from Fowler (1944):
In writing this straightforward and workmanlike biography
of his grandfather (the book was finished before the war and
delayed in publication) Mr. Walter Jerrold has aimed at doing
justice to Douglas Jerrold ....
The parenthetical idea has no bearing on the sentence!
Parentheses enclose numbers in an enumeration within a
sentence:
The scatterometer is separated into (1) a gimbal, (2) a
transmitter-receiver assembly, and (3) rack-mounted electronics.
70 Back to Top
When the enumerated list is displayed, a period following the
number is sufficient to set it off (Skillin et al. 1974; and Chicago
Press 1982):
The scatterometer is separated into
- A gimbal
- A transmitter-receiver assembly
- Rack-mounted electronics
Ebbitt and Ebbitt (1982) neatly explain use of parentheses with
other punctuation marks as follows:
When a complete sentence in parentheses comes within a
sentence (notice the punctuation of this one), it needs neither a
capital letter nor a period. Commas and other marks of punctuation
in the main sentence always follow the parenthesis (as here
and in the preceding sentence). (A sentence in parentheses, like
this one, that does not stand within another sentence has the end
punctuation before the closing parenthesis.)
Punctuation (for example, question marks, quotation marks) of the
ideas within parentheses remains within parentheses, while
punctuation of the main sentence remains outside, almost always after
the closing parenthesis rather than before an opening parenthesis. A
comma precedes an open parenthesis if the parenthetical matter
clearly limits the word following it (Skillin et al. 1974):
Despite these differences, (digital) image-gathering
systems can be compared with optical imaging systems.
3.11. Period
The period is a mark of separation. Its primary purpose is to
separate complete thoughts, to mark the end of declarative and
imperative sentences. (Interrogative sentences end with a question
mark; exclamatory, with an exclamation point.) The key word here is
complete; a period should be used only after a sentence
complete with subject and predicate.
Do not use a period after headings on separate lines
(run-in headings are often separated from text by a period), after
running heads, after table titles, or after items in an enumerated,
displayed list unless one or more of the items are complete
sentences:
The purposes of this report are
- To evaluate the performance of instruments
- To expand the data base
We can define the requirements of the power converter as
follows:
- .Energy conversion should be high.
- Efficiency should be independent of laser wavelength.
71 Back to Top
It is customary to end figure captions with a period
whether or not they are complete sentences:
Figure 1. Computing scheme for algorithm.
Figure 1. Concluded.
A period may follow abbreviations except those for units of
measure. The trend is away from periods for abbreviations (Skillin et
al. 1974; and Chicago Press 1982), but they are retained for many
word abbreviations, particularly those that may be confused with an
unabbreviated word:
Periods are not used for abbreviations of units of measure
(except inch), for acronyms, or for contractions (with
apostrophe):
ft
|
cm
|
lb
|
NASA
|
V/STOL
|
nat'l
|
A period does follow the abbreviation for inch
1 in.
|
but
|
in/hr
|
14 lb/in.
|
|
in-lb, 6-in-wide
|
Whether or not to end an abbreviation with a period is best
determined by consulting
G.P.O. Style Manual
Webster's Collegiate or Unabridged Dictionary
3.11.2. Conventional Uses of the Period
The period is so useful for separation that several conventional
uses exist:
A period precedes decimal numbers:
A period separates dollars and cents:
In enumerations, a period usually follows the number or
other designator:
Volume I. Theory
Figure 2. Response times.
The options are
- Optical rectification
- Laser-driven magnetohydrodynamics
- Laser photovoltaics
72 Back to Top
Periods are used in section numbers
- Introduction
This subject is discussed in section I.A.1 of reference 3 and
in section 5.2 of this paper.
3.11.3. Use With Other Marks
A period may be used only with quotation marks, parentheses and
brackets, and points of ellipsis, but not with other marks unless the
period marks an abbreviation:
(In this fig., the dots denote dots)
(e.g., decimal numbers)
(Why include the following three pp.?)
But a period is never repeated after an abbreviation:
I prefer the abbreviation Ms.
Place periods before closing quotation marks.
The operator presses the letter n to indicate
"no" and the letter y to indicate "yes."
The word pultruded is defined to mean the opposite of
"extruded."
Generally periods are placed outside closing parentheses;
place the period inside only when a complete parenthetical sentence
does not stand within another sentence (see section parens):
(Parenthesized sentences, like this one, that do not
stand within other sentences have a period before the closing
parenthesis.)
3.12. Points of Ellipsis
Points of ellipsis (three evenly spaced periods) are used in
formal writing to indicate an omission from quoted matter:
This combination caused Wright to wonder whether "since
the interference velocities due to . . . walls are of opposite
signs . . ., opposite effects might be so combined in a slotted
tunnel as to produce zero blockage."
Ellipsis points should not be used (Chicago Press 1982)
- Before or after a quotation run in the text
- Before a block quotation beginning with a complete
sentence
- After a block quotation ending with a complete sentence
Points of ellipsis are commonly used with other punctuation marks.
Ellipsis points in a quotation always occur within the quotation
marks.
73 Back to Top
Punctuation in the quote before or after the ellipsis should be
retained if it will enhance meaning:
"The gangs were of all races and conditions: . . . part
of the huge compost of America."
"In the city of Hampton alone, hundreds of families emigrated .
. ., scores were made jobless, houses were empty and business
generally suffered."
The terminal period (at the end of a sentence) is always
retained before an ellipsis and may be retained after ellipsis to
enhance meaning:
Period before ellipsis
|
|
At a Mach number of 0.98, ``the needle of the Mach meter
took an abrupt jump past M = 1.0 and went against the
peg, which is a distance equal to about 0.05 in Mach number
past 1.0. . ..''
|
Period after ellipsis
|
|
``When the Mach number went off the scale, the pilot shut
down all cylinders . . .. Preliminary NASA data work-up
indicates that a Mach number of 1.06 was reached.''
|
Note the difference in spacing of periods before and after points
of ellipsis.
3.13. Question Mark
The purpose of the question mark is to terminate a direct
question, whether the question is an independent sentence, a clause
within a sentence, or a direct quotation:
What system identification procedure should be used for a
statically unstable aircraft?
The question addressed by this research project is, What system
identification procedure should be used for a statically unstable
aircraft?
In reference 2, Jones asks, "What system identification
procedure should be used for a statically unstable aircraft?"
When the direct question occurs within a sentence (as in the
second example above), the author may or may not choose to capitalize
the first word of the question.
When the question is a single word, such as when,
how, or why, within a sentence, neither a question mark
nor a capital is necessary; the word is often italicized:
The announcement should answer the questions who,
what, where, when, and why.
A question mark should not follow an indirect question:
This research project addresses what system
identification procedure should be used for statically unstable
aircraft.
74 Back to Top
A question mark may be used with other marks of punctuation as
follows:
The question mark supersedes a period or comma.
A question mark precedes a closing quotation mark or
parenthesis only if it is part of the quoted or parenthetical
matter:
Because of the ambiguous use of the slash, the reader
might well ask the question, What is meant by "molecular/atomic
collision"?
The obvious question is, how accurate is this estimate
(compared with the accuracy of the input measurements)?
When the question mark ends a sentence, the period is, of
course, omitted. When the question mark does not end the sentence, it
should never be followed by a comma; if required, a semicolon may
follow a question mark:
The obvious question is, how good is this estimate? and
equation (6) provides a tool for answering it.
The reader might well ask the question, What is meant by
"molecular/atomic collision"?; the slash gives no clue to the
meaning.
3.14. Quotation Marks
Quotation marks are used to enclose words quoted from another
source, direct discourse, or words requiring differentiation from the
surrounding text. Since they enclose, they always come in pairs. They
can also be overused and render a text visually hard to read.
Double quotation marks (" ") are used most of the time. Single
quotation marks (' ') are used only within double quotation
marks.
3.14.1. Quoted Material
If a document quotes extensively from other sources, consult an
authority, such as Chicago Press (1982), chapter 10, for details of
correctly setting up quotations.
Quotation marks enclose material taken verbatim from another
source. The quote can be of any length, from a phrase to several
paragraphs:
Diehl argued that a transonic research plane was
necessary to demonstrate that the sound barrier was "just a steep
hill."
As Richard P. Hallion has explained: "They gave the fuselage a
pointed nose then gradually thickened the body--that is, increased
the cross-sectional area--until the fuselage reached its maximum
diameter near the middle."
The source of a quote should always be clear, either from
the context or with a reference citation.
75 Back to Top
Long quotations are usually set off from the text and set
in smaller type if typeset. Such block quotations are not enclosed by
quotation marks:
Stack allowed Whitcomb to present his area rule at the
next meeting of Langley's elite technical seminar.
At the end of presentation there was
silence. Finally, Adolf Busemann stood up. Turning to his
colleagues, the pioneer of sweptwing technology remarked, "Some
people come up with half-baked ideas and call them theories.
Whitcomb comes up with a brilliant idea and calls it a rule of
thumb."
Note the double quotes within the quotation. If the quotation had
not been set off but had been run in the text and enclosed in
quotation marks, then single quotes would have enclosed Busemann's
remark.
3.14.2. Words Requiring Differentiation
Quotation marks may enclose words that need to be differentiated
from the text in order to make meaning clear. Italics are used for
much the same purpose (see section 3.9.3) and are sometimes
interchangeable with quotation marks.
Enclose in quotes a word or phrase whose meaning is being
referred to:
The operator presses the letter nto indicate "no"
and the letter y to indicate "yes."
The word pultruded is defined to mean the opposite of
"extruded."
Words used simply as words are usually italicized:
A colon is not used after that is, for example,
or such as.
Enclose words or phrases following entitled, the term,
marked, designated, classified, named, enclosed, cited as, referred
to as, or signed, but do not enclose an expression
following known as, called, or so-called unless the
expression is slang (G.P.O. 1984). Of course, an italicized phrase or
word (for example, a title) would not be further differentiated with
quotation marks.
Do not routinely enclose slang or technical jargon (if
used) in quotation marks, unless it is expected to be foreign to the
vocabulary of the reader:
Quotes unnec.
|
The pilot "captured" the glide slope at an altitude of
300 m.
|
Quotes OK
|
Recently, "cepstrum" analysis has come into prominence;
the name is derived from inverting the first four letters in
spectrum.
|
Such terms are normally quoted only the first time they are
used.
76 Back to Top
Enclose in quotation marks coined terms or technical terms
used in a nonstandard way:
Synoptic data (or "snapshots" of global parameters) are
required.
If the results satisfied a set of general, and sometimes
intuitive, criteria, they were accepted as being "good."
Such terms are normally quoted only the first time they are
used.
Enclose in quotation marks the titles of parts (sections,
chapters) of a report or book and the titles of published papers,
articles, etc., that are not italicized (see section 3.9.5):
The aircraft is described in more detail under the
section entitled "Flight Facility."
The runway is marked in accord with FAA circular AC
150/5300-2B, "Airport Design Standards---Site Requirements for
Terminal Navigational Facilities."
Langley drops quotation marks in reference lists and
bibliographies; the number of quotes in these sections makes them
unsightly and hard to read.
3.14.3. Use With Other Marks
Quotation marks may be used with all other marks of
punctuation.
- Closing quotation marks always follow commas and periods,
regardless of the context.
- Closing quotation marks always precede semicolons and colons
(because they are always dropped at the end of quoted
material).
- Closing quotation marks always follow points of ellipsis
indicating omitted matter in the quote; ending a quote with
ellipsis is rarely necessary.
- Other marks of punctuation (parentheses, question mark) are
placed outside quotation marks if they are not a part of the
quoted matter.
3.15. Semicolon
The semicolon separates coordinate clauses, long internally
punctuated elements of series, explanatory phrases and clauses, and
elliptical clauses. The semicolon denotes nearly a full stop; thus,
its uses are as much a matter of personal choice as of correct
punctuation.
3.15.1. Coordinate Clauses
Coordinate clauses may be joined by a semicolon.
If coordinate clauses are not joined by a coordinate
conjunction, they must be joined by a semicolon:
The first two flight runs for each pilot were treated as
practice; only the last four runs were used in the analysis.
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If coordinate clauses are joined by a coordinate
conjunction but the clauses are long, complicated, or internally
punctuated with commas, they may be separated by a semicolon:
The pilots unanimously preferred the new display format
because of the steadiness of the horizon, runway image, and pitch
grid during turbulence; and they felt that this steadiness
resulted in less distraction and better situational awareness.
If coordinate clauses are joined by a conjunctive adverb
( however, thus, therefore, hence), a semicolon (or a period)
must precede the conjunctive adverb:
The differences were generally about 11 percent; however,
larger differences occurred at
= 15.
Whether a period, semicolon, or comma is used between clauses is a
matter of style. In Writer's Guide and Index to English,
Ebbitt and Ebitt discuss semicolons and style: "Semicolons are
usually more suitable in the longer, more complicated sentences of
formal styles dots. In general styles commas are often used where
semicolons might appear in formal writing, or else clauses that could
be linked by semicolons are written as separate sentences." A
semicolon slows the pace and has more separating force than a comma
while still tending to join clauses; a period simply
separates sentences. The semicolon is particularly effective
between contrasting clauses:
One pilot performed slightly better with the
attitude-aligned display; the other pilot performed much worse.
A dash (section 3.6.2) or colon (section 3.4.1) may also separate
two clauses when the second amplifies or restates the first. The
colon is more formal and has more introductory force than the
semicolon, and the dash is more emphatic than the semicolon.
3.15.2. Series
When elements of a series are long, complex, or internally
punctuated with commas, separating the elements with commas may not
make meaning clear.
Semicolons may separate elements of a series that are
complex or require internal commas:
Committee members were H. Melfi, NASA Goddard Space
Flight Center, Greenbelt, Maryland; A. L. Carswell, York
University, North York, Canada; and E. V. Browell, NASA Langley
Research Center, Hampton, Virginia.
Remember that a semicolon signals nearly a full stop. Semicolons
may clarify the elements of a series, but at the same time disrupt
the flow:
The goal was to accelerate application of composites to
primary structures in new civil transport aircraft by development
of design techniques for empennage, wing, and fuselage structures;
dissemination of technology throughout the transport industry; and
extensive flight service evaluations.
78 Back to Top
Another way to clarify the series might be devised, for example,
enumeration or rearrangement of elements of the series:
The goal was to accelerate application of composites to
primary structures in new civil transport aircraft by (1)
development of design techniques for empennage, wing, and fuselage
structures, (2) dissemination of technology throughout the
transport industry, and (3) extensive flight service evaluations.
The goal was to accelerate application of composites to primary
structures in new civil transport aircraft by dissemination of
technology throughout the transport industry, extensive flight
service evaluations, and development of design techniques for
empennage, wing, and fuselage structures.
3.15.3. Explanatory Phrases and Clauses
In technical writing explanatory information often follows such
introductory phrases as that is, namely, for example, in other
words, for instance.
A semicolon must precede a phrase like that is,
namely, and for example when it introduces an independent
clause:
Some random processes are reasonably independent of the
precise time; that is, measurements made at different times are
similar in their average properties.
3.15.4. Elliptical Constructions
When commas are necessary to indicate the omission in an
elliptical construction, a semicolon separates the elliptical
clauses:
Wind speed is obtained from antenna brightness
temperature; rain rate, from the brightness temperature difference
at two frequencies; and wind vector, from radar cross section.
Of course, if the commas are unnecessary to indicate omission, the
semicolon can be replaced by a comma so long as the clauses are
joined by a conjunction:
|
Wind speed is obtained from antenna brightness
temperature, and wind vector from radar cross section.
|
But
|
Wind speed is obtained from antenna brightness
temperature; wind vector, from radar cross section.
|
3.15.5. Use With Other Marks
Semicolons always follow closing parentheses and quotation marks;
semicolons are always dropped at the end of quoted material (Chicago
Press 1982).
79 Back to Top
3.16. Slash
A slash, also called solidus or virgule, can be
correctly used (1) in and/or, (2) in fractions (x/y), (3) to
indicate per (m/sec), and (4) when quoting poetry.
Although most usage and grammar authorities do not acknowledge use
of the slash in a temporary compound, it is being widely used to
indicate temporary compounds. In drafts of NASA reports, we
frequently find such constructions as
hoop/column antenna
boundary-layer/shock-wave interaction
matrices/vectors
lateral/directional characteristics
In the first example (hoop/column), those coining the new
technical term seem to have chosen (erroneously) to use a slash
rather than a hyphen; however, this term, meaning a combination of a
hoop and a column, has been widely used with the slash. In the second
example ( boundary-layer/shock-wave interaction), the slash is
being used as an en dash, or ``long hyphen.'' In the third example
(matrices/vectors), the slash indicates alternatives, a usage
that Tichy and Fourdrinier (1988) accept with caution. In the last
example (lateral/directional), the slash is being used in a
unit modifier that has been hyphenated for years.
These four examples illustrate our objection to use of the slash
in temporary compounds: Its meaning is not clear.
We therefore prefer that the slash be changed to a
hyphen,
The 15-m hoop-column antenna is a deployable and
restowable structure.
to an en dash,
These phenomena result from
shock-wave--boundary-layer interaction.
or to and, or, or and/or,
Operator splitting is additive decomposition of some
matrices and vectors in the model.
Of course, some technical terms have become standard with the
slash (for example, V/STOL, stall/spin).
A term that is accepted as standard with a slash may be
used with the slash.
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