Chapter 1. Grammar
1.1. Grammar and Effective Writing
All writing begins with ideas that relate to one another. An
author chooses words that express the ideas and chooses an
arrangement of the words (syntax) that expresses the relationships
between the ideas. Given this arrangement of words into phrases,
clauses, and sentences, the author obeys grammar and punctuation
rules to form a series of sentences that will impart the ideas.
English rules of grammar originated in antiquity, but over
centuries have evolved according to usage and are still changing
today. Thus, grammar rules may change and may be inconsistent, but
usually have a functional basis. This functional attitude toward
grammar, and punctuation, is described in Effective Revenue
Writing 2 (Linton 1962). A rule of grammar or punctuation with a
functional basis will not prevent effective statement of ideas, nor
will following all the rules ensure effective writing.
Effective writing requires good syntax, that is, an effective
arrangement of sentence elements. Obviously, an editor is responsible
for ensuring that a consistent and correct set of grammar and
punctuation rules have been applied to a report (a process often
called copy editing). However, language and substantive edits, as
defined by Van Buren and Buehler (1980), involve revision of
sometimes perfectly grammatical sentences to improve effectiveness of
sentence structure. This chapter discusses grammar, and the next
chapter concerns sentence structure with emphasis on methods of
revision.
According to Webster's Ninth New Collegiate Dictionary,
grammar means "the study of the classes of words, their
inflections [changes in form to distinguish case, gender, tense,
etc.], and functions in a sentence." An abundance of good,
detailed grammar, writing, and usage books are available. This
chapter is not meant to be a definitive grammar reference. It is
intended to address grammatical problems often encountered in
technical documents and to indicate preference when grammar
authorities do not agree. Please refer to the books cited in the
References section and others to complement and clarify the
discussions that follow.
1.2. Nouns
Nouns change form to indicate case and number. The number of a
noun is usually not a problem (though the number of pronouns and
verbs corresponding to the noun may be). The three possible cases are
nominative, objective, and possessive. In English, nominative and
objective case nouns have the same form.
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1.2.1. Possessive Case
At Langley, the preferred rules for forming possessives are as
follows (G.P.O. 1984; and Rowland 1962):
Form the possessive of a singular or plural noun not ending
in s by adding 's.
Form the possessive of a singular or plural noun ending in
s by adding an apostrophe only:
Singular
|
Plural
|
|
man's
|
men's
|
horse's
|
horses'
|
Jones'
|
Joneses'
|
Form the possessive of a compound noun by adding 's
to the end of the compound:
sister-in-law's home
John Doe, Jr.'s report
patent counsel's decision
Indicate joint possession by adding 's to the last
element of a series; indicate individual possession by adding
's to each element:
Wayne and Tom's office (one office)
editor's, proofreader's, and typist's tasks
Some authorities (for example, Skillin et al. 1974; and Bernstein
1981) partially disagree with the second rule above. They state that
the possessive of a singular proper noun is formed by adding
's even when the noun ends in s (for example, Jones's);
however, a triple sibilant is always avoided (for example,
Jesus').
1.2.2. Possessive of Inanimate Objects
In the past, the possessive case ('s) was not acceptable
for inanimate nouns. Instead the preposition of was preferred, that
is, strength of the laminate rather than laminate's
strength..
Exceptions to this rule were inanimate words representing a
collection of animate beings (for example, company's profits,
university's curriculum) and words expressing measure or time (for
example, 2 hours' work). Current practice is to dispense with both
the 's and the of (Skillin et al. 1974):
company profits
university curriculum
laminate strength
2 hours work
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In fact, the use of 's on an inanimate object is no longer
taboo, particularly if the object has some lifelike qualities
(Bernstein 1981):
computer program's name
Earth's rotation
Whether an 's can properly be added to an inanimate noun
seems to be a matter of idiom. We would not say, for example,
systems' analyst
table's top
1.3. Pronouns
All pronouns must have an antecedent (the noun they replace) with
which they agree in number, gender, and person. In addition, some
pronouns change form to indicate nominative, objective, and
possessive case (for example, he, him, his).
An apostrophe is never used to form possessive case
pronouns.
1.3.1. Antecedents
Most grammatical errors involving pronouns result from the lack of
a clear antecedent. The following sentences suffer from this
problem:
He foresaw aircraft applications and thus emphasized
rectilinear motions.
This causes complicated integral equations for other types
of motion.
The boundary condition becomes a source term, which
permits use of the
Green function.
Required surface pressures are obtained in several ways, for
example,
from blade element theory or experimental measurements. Whatever
the
technique, it is usually available.
In the first two sentences the pronouns this and
which refer to the idea of the previous sentence or clause and
do not have a noun antecedent. The Writer's Guide and Index to
English (Ebbitt and Ebbitt 1978) states that this "broad
reference" usage of pronouns is acceptable in "general" writing, but
should be avoided in "formal" writing. The danger of broad reference
is that the antecedent (whether a noun or a clause) may not be clear.
In the second sentence above, which appears to refer to
term. The following revisions would be preferable:
He foresaw aircraft applications and thus emphasized
rectilinear motion.
This emphasis causes complicated integral equations for other
types of
motion.
Because the boundary condition becomes a source term, the
Green
function can be used.
In the third sentence, it is much too distant from its
antecedent, pressures. Because of this distance, the pronoun
does not agree in number with its antecedent.
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Bernstein (1981) discusses ambiguous or nonexistent antecedents
under "Pronouns" and under particular words, for example, "Each" and
"None."
Grammatical errors involving pronoun antecedents can be
avoided very simply: check every pronoun for a clear, appropriate
antecedent and then ensure agreement between antecedent and
pronoun.
1.3.2. Personal Pronouns
First person pronouns
Tichy and Fourdrinier (1988) attribute the pervasiveness of
passive voice in technical writing to evasion of first person
pronouns (I, we). In the early 1900's, first person
pronouns were banished from technical writing to obtain objectivity;
however, Tichy and Fourdrinier effectively demonstrate that
objectivity is not always attained. Writing authorities no longer
forbid, and sometimes encourage, the use of first person pronouns
(CBE 1978; AIP 1978; Houp and Pearsall 1984; and Mills and Walter
1978). Thus, we in technical documents cannot be condemned,
particularly when the opinion of the author (and a research staff) is
being expressed:
We believe that this effect is due to nozzle aspect
ratio.
This use of we, meaning "I and others," should be
distinguished from the editorial we, meaning "you readers and
I" (Ebbitt and Ebbitt 1982). In technical documents the editorial we
is often used in mathematical presentations:
Now we define a recursive relation for the (k +
l)th iteration:
P k + 1 =
(XT /
k
Xk )
-1
Tichy and Fourdrinier (1988) recommend that the antecedent of
we always be made clear. They also offer advice on when to use
first person pronouns and when not to.
Gender
Third person singular pronouns change form to indicate gender
(he, she). When the pronoun could refer to either sex
or when the antecedent's sex is unknown, the masculine pronoun is
grammatical. However, in recent years, objections have been raised to
this grammatical rule.
It is preferred practice to avoid the masculine pronoun
when the antecedent may be feminine. Often the antecedent can be made
plural:
Poor
|
An editor must have guidelines on which to base
his
revisions.
|
Better
|
Editors must have guidelines on which to base their
revisions.
|
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Or the wording of the sentence can be changed:
Poor
|
The listener may not fully perceive the sound because
his ear has a critical summation time of 1 sec.
|
Better
|
The listener may not fully perceive the sound because
the human ear has a critical summation time of 1 sec.
|
1.3.3. Relative Pronouns
Relative pronouns function not only as pronouns but also as
conjunctions. The relative pronoun replaces a noun in a dependent
clause and connects the clause to the rest of the sentence.
Antecedents of relative pronouns
Who and whom refer to persons.
Which refers to things.
That refers to things and in rare instances may
refer to persons.
Whose, the only possessive case relative pronoun,
may refer to either persons or things according to Bernstein (1981).
Other grammar authorities disagree and condemn the use of
whose to refer to inanimate nouns. We prefer whose when
of which would be awkward:
Awkward
|
A low-cost process has been developed for making
alumina,
the limited availability and cost of which have
previously
inhibited its widespread use.
|
Better
|
A low-cost process has been developed for making
alumina,
whose limited availability and cost have previously
inhibited
its widespread use.
|
Awkward
|
The attenuation is accompanied by an echo the
amplitude
of which is above the background level and the position
of
which is related to the depth of the region.
|
Better
|
The attenuation is accompanied by an echo whose
amplitude
is above the background level and whose position is
related
to the depth of the region.
|
Which versus that
Which is always used in a nonrestrictive relative
clause (one that could be omitted without changing the meaning of the
basic sentence):
The most common examples of panel methods are the
aerodynamic codes of Hess and Smith (ref. 26), which were
originally developed for nonlifting surfaces.
Which may also be used in a restrictive relative clause.
Note that proper punctuation of restrictive and nonrestrictive
clauses is vital: commas enclose nonrestrictive clauses, but never
enclose restrictive clauses (see section 3.5.2).
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That is preferred for restrictive (or defining) relative
clauses (Bernstein 1981):
The most common examples of panel methods are the
aerodynamic codes that Hess and Smith (ref. 26) designed for
nonlifting bodies.
There are three exceptions to the use of that to introduce
a restrictive clause:
Which must be used after a preposition (Bernstein
1981):
The shading in figure 2 indicates elements in which
fibers have failed.
Which is used after the demonstrative that
(Bernstein 1981):
The most commonly used aerodynamic code is that which
Hess and Smith (ref. 26) designed for nonlifting bodies.
Which sounds more natural when a clause or phrase
intervenes between the relative pronoun and its antecedent (Fowler
1944):
Finite bodies can undergo motions (such as
spinning) which complicate the equations.
Omission of that
That can sometimes be omitted from restrictive relative
clauses, but this omission is not recommended:
Correct
|
The model they analyzed is the most realistic one
studied.
|
Better
|
The model that they analyzed is the most realistic one
studied.
|
Who versus whom
Who (and its indefinite derivative whoever) is the
only relative pronoun that changes form to indicate case
(who, whom, whose). When a relative clause is
inverted, we have difficulty determining whether the pronoun is in
nominative case (who) or in objective case (whom). The
easiest way to resolve such questions is to change the relative
clause to an independent clause by substituting a third person
personal pronoun for the relative pronoun. For example, in the
questionable sentence
Information derived from this contract may be transmitted
to those who the Defense Department has cleared to
receive classified information.
change the relative clause to an independent clause:
The Defense Department has cleared them to receive
classified information.
The sentence requires a third person pronoun in objective case
(them), so the relative pronoun must also be in objective case (...
those whom the Defense ... ).
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1.3.4. Demonstrative Pronouns
Demonstrative pronouns refer to something present or near
(this, these) or to something more remote (that,
those). Technical writing tends to exhibit two types of
problems involving demonstrative pronouns: broad reference (see
section 2.2.1) and incomplete comparison (see section 2.5.2).
Broad reference
The demonstrative this is often used to refer to the idea
expressed in the previous sentence, a practice to be avoided in
formal writing (Ebbitt and Ebbitt 1982). For example,
The entire noise prediction methodology for moving bodies
becomes autonomous. This means that improved models can be
incorporated simultaneously in pressure and noise calculations.
Most loads could be reduced 0.8 percent if voltage was more
closely regulated. Nonessential loads such as payloads could take
advantage of this, but essential loads could not.
This type of construction is sometimes vague and usually
unnecessary. Often the demonstrative pronoun can be deleted:
The entire noise prediction methodology for moving bodies
becomes autonomous. Thus, improved models can be incorporated
simultaneously in pressure and noise calculations.
Or the antecedent can be clarified:
Most loads could be reduced 0.8 percent if voltage was
more closely regulated. Nonessential loads such as payloads could
take advantage of voltage regulation, but essential loads could
not.
Incomplete comparison
Demonstrative pronouns can often be used to complete vague
comparisons:
Poor
|
The errors in this prediction are greater than in table
III.
|
Better
|
The errors in this prediction are greater than those in
table III.
|
But make sure that the antecedent and meaning are clear:
Unclear
|
West's results were in better agreement with ours than
those of Long et al.
|
Either
|
West's results were in better agreement with ours than
those of Long et al.
|
Or
|
West's results were in better agreement with ours than
with those of Long et al.
|
See section 2.5 for further discussion of comparisons.
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1.4. Verbs
Verbs, the only words that can express action, change form to
indicate person, tense, mood, voice, and number.
1.4.1. Tense
Verbs change form to indicate tense, or time that an action or
state of being takes place. English has six tenses: present, present
perfect, past, past perfect, future, and future perfect. Each of the
six tenses has a progressive form indicating a continuing action.
(See Text 4 of Effective Revenue Writing 1, IRS 1962.) Writing
authorities do not specify exactly which tenses should be used in a
technical document, but they universally agree that shifts in tense
should occur only when the time of the action changes. In other
words, the point of view of a report with respect to tense must be
consistent.
The relationship between point of view and verb tense can be
understood in terms of the four elements of discourse (Buehler
1970):
- Exposition (explains how and why things happen)
- Narration (tells what happened)
- Description (gives a mental image)
- Argumentation (convinces by reasoning)
The elements are quite often mixed. For example, in the Results
and Discussion section, behavior of models or specimens (narration)
might be discussed alang with presentation of results in tables and
figures (description) and explanation of results (exposition).
Narration is usually in past tense while description and exposition
are usually in present tense. Consistency in tense does not mean that
all sentences are in the same tense; it means that sentences
expressing the same point of view (or element of discourse) are in
the same tense. Avoid shifting back and forth between points of view
by grouping material with a consistent viewpoint; but when the
viewpoint does shift, shift the tense accordingly.
Tenses of independent clauses of report
There are no firm rules concerning tense of various sections in a
report. However, if an author is inconsistent in tense, the following
guidelines might be helpful to the editor:
The Summary is usually in past tense.
Past research (for example, in references) is usually
described in past tense.
Permanent facilities are usually described in present
tense.
Experimental procedures and apparatus for a particular
study are usually described in past tense.
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Behavior of models, specimens, etc., during the study is
usually expressed in past tense, and results presented in the
report's illustrative material are expressed in present tense:
Typical fracture profiles are shown in figure 21. These
profiles show that fracture mode changed with cyclic exposure. The
specimens failed ...
As shown in figure 10, the autorotative rolling moment is a
nonlinear function of roll rate, so that as spin rate increased,
the propelling moments became equal.
Explanation of why results occurred are in present
tense:
The data failed to provide any reasonable estimates for
Cnr. This failure can be
attributed to the small excitation of yawing velocity.
The Concluding Section is usually in past tense except that
conclusions (that is, deductions thought to be universally true
independent of the specific conditions of the investigation) should
be in present tense.
The Abstract is usually in present tense.
Sequence of tenses
The logical time relation between the various verbs and verbals in
a sentence is expressed by shifts in the tense of these verbs and
verbals. Sequence of tenses is a very complicated subject, which is
discussed in almost every grammar and writing book. Only the basic
guidelines are given here; for a more complete understanding, refer
to such reference books.
When the principal verb is in a present or future tense,
subordinate verbs may be in any tense:
The data indicate that lift increases with angle of
attack up to =
35°.
The data indicate that the specimen failed in a noncumulative
mode.
The data indicate that propellers will have a place as a
propulsive device of the future.
When the principal verb is in a past tense, the subordinate
verb must be in a past tense unless the subordinate clause expresses
a universal truth or an action that is still continuing:
The data indicated that lift increased with angle of
attack up to =
35°.
Previous studies had indicated that alumina is a suitable fiber
for reinforcement.
The present tense forms of verbals refer to action
occurring at the same time as the main verb; the past tense or
perfect tense forms of verbals refer to action occurring before the action of
the main verb. This
principle is most easily seen for participles:
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Photographs indicating nearly laminar flow
justified this assumption.
Photographs taken during an earlier test justified this
assumption.
1.4.2. Mood
The three moods in English are indicative, imperative, and
subjunctive. Almost all verbs in technical documents are indicative.
Imperative mood is sometimes used in instructions or descriptions of
procedures. Subjunctive mood is rarely used and seems to be
disappearing from English usage. However, there are two situations
when the subjunctive should be used (Bernstein 1981):
Subjunctive mood is used to indicate a command, suggestion,
recommendation, or requirement:
The console operator instructed that the preflight
inspection be repeated.
The committee recommends that this research be
continued.
Subjunctive mood is used to indicate a condition contrary
to fact or highly improbable:
If the integral were not singular, the question
could be solved easily.
Up to now, all discontinuous fiber-reinforced composites have
low ductility. If their ductility were improved, they would
be highly attractive materials for aircraft applications.
The subjunctive should be used only when the author wishes to
imply strong doubt. Notice the subtle change in attitude when the
subjunctive is not used in the above example:
If their ductility was improved, they would be
highly attractive materials for aircraft applications.
1.4.3. Voice
The voice of a verb indicates whether the subject is performing
the action (active) or receiving the action (passive). Writing
authorities overwhelmingly prefer active voice because it is direct,
clear, and natural. Overuse of passive voice weakens style and
obscures responsibility. This preference for active voice is not a
condemnation of passive voice. Tichy and Fourdrinier (1988) list five
situations when the passive voice is appropriate:
When the actor is unimportant, not known, or not to be
mentioned
When the receiver of the action should be emphasized
When the sentence is abrupt in active voice
When variety is needed in an active voice passage
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When a weak imperative is needed (for example, "The figures
should be corrected quickly" )
The first two items justify much of the passive voice in technical
documents. See section 2.2.2 for a discussion of revising passive
voice sentences to make them active voice.
1.4.4. Verb Number
A verb must agree in number with its subject. This is a simple and
absolute rule. However, verb-noun disagreements (in number) are
common grammatical errors, sometimes caused by words intervening
between the subject and verb and sometimes caused by difficulty in
determining the number of the subject.
Some nouns have confusing singular or plural forms, for
example,
aeronautics, sing.
|
equipment, sing.
|
apparatus, sing.
|
hardware, sing.
|
apparatuses, pl.
|
phenomena, pl.
|
data, pl. 1
|
criteria, pl.
|
Consult the dictionary or a usage book when there is a question
concerning the number of a particular noun.
Subjects joined by coordinate conjunctions
Subjects joined by and, whether singular or plural,
require a plural verb.
Singular subjects joined by or or nor require
a singular verb.
When a singular subject and a plural subject are joined by
or or nor, the verb agrees in number with the subject
nearer to it.
When subjects are joined by and/or, the number of
the verb depends on the interpretation of and/or. Either a
singular or plural verb can be justified. Bernstein ( 1981 )
considers and/or a "monstrosity" and recommends that it be
avoided. Often either and or or alone is
sufficient.
Subjects with intervening phrases
Phrases that intervene between the subject and verb do not affect
number of the verb; it always agrees with the subject:
Damping ratio as well as frequency agrees with the
experimental values.
This error plus any other systematic errors appears in the
output of the instrument.
1 Authorities disagree on the number of
the noun data. Bernstein (1981) takes the traditional view
that it is a plural noun, but Tichy and Fourdrinier (1988), Ebbitt
and Ebbitt (1982), and IRS (1962) consider it to be a collective noun
either singular or plural depending on its meaning. We prefer that
data be plural in Langley reports.
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Collective subjects
A singular collective subject, which names a group of people or
things, is treated as singular when the group is considered a unit or
as plural when the members of the group are considered
individually:
Langley's research staff is well-known for its
achievements in aeronautics.
Langley's research staff do not all publish their results in
report form.
The number of such words as most, all,
some, half, part, or percent is governed
by the number of the noun in the phrase that follows, or that could
follow, them:
Most of the measurements contain this error.
Most of the disagreement between the plots is attributed to
this error.
Six percent of the chord has laminar flow.
Of the subjects tested, six percent rate all the noises
acceptable.
When a number is used with a plural noun to indicate a
single measurement, a singular verb is required:
Twenty liters of fuel has passed through the combustion
system.
When such a subject is thought of as individual parts, a plural
verb is appropriate:
Twenty milliliters of water were added, one at a time, to
the solution.
Compound clauses with auxiliary verbs omitted
In compound sentences with passive voice verbs, the auxiliary
verbs are sometimes erroneously omitted:
The wing plate was fabricated from nickel 201, its
surface polished, and nickel rods welded to its edge.
The omission of auxiliary verbs is grammatical unless the
subjects change number (Rowland 1962). The above sentence should
be
The wing plate was fabricated from nickel 201, its
surface polished, and nickel rods were welded to its edge.
1.5. Adjectives
Since modifiers make up the bulk of most writing, their placement
is very important to sentence structure.
In contrast to adverbs, adjectives are naturally placed near the
noun or pronoun that they modify. Single-word adjectives and unit
modifiers precede the noun and adjective phrases and clauses follow
it. See section 2.2.3 for a discussion of placement of modifiers.
See section 2.5.1 for discussion of the degree (positive,
comparative, and superlative) of adjectives.
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1.5.1. Articles
Indefinite articles a and an
The indefinite article a precedes a word beginning
with a sounded consonant, and an precedes a word beginning
with a vowel sound.
Whether a or an should precede an
abbreviation or acronym depends not on its initial letter but on how
the author expects it to be read (Bernstein 1981). For example, most
people read "M.A." as letters rather than as "Masters of Arts," so
"an M.A. degree" is appropriate. Likewise, we prefer "an NACA
airfoil." However, "NASA" is not usually read as letters, so we
prefer "a NASA airfoil."
Articles with coordinate adjectives
Whether or not articles are repeated before coordinate adjectives
affects meaning (Rowland 1962).
If coordinate adjectives each refer to different things or
persons, articles are repeated when the modified noun is singular and
are not repeated when the modified noun is plural:
Wrong
|
The transverse and shear strain is calculated for each
specimen. (two strains)
|
Correct
|
The transverse and the shear strain is calculated for
each specimen.
|
Or
|
The transverse and shear strains are calculated for each
specimen.
|
If coordinate adjectives refer to one thing or person, the
article is not repeated:
Wrong
|
A more nonlinear and a lower stress-strain curve resulted
from the test. (one curve)
|
Correct
|
A more nonlinear and lower stress-strain curve resulted
from the test.
|
Omission of articles
There is a trend in modern writing, particularly journalism, to
omit articles. Langley has traditionally preferred this "elliptical
style" for symbol lists, figure captions, headings, and titles:
u ratio of
[the] wing mass to [the] mass of air in
[a] truncated cylindrical cone enclosing [the]
wing
Figure 1. Effect of leak area on pressures, heating rates, and
temperatures in [the] cove and at [the]
bulkhead.
Spectral Broadening by [a] Turbulent Shear Layer
Bernstein (1981) calls elliptical style a "disfigurement of the
language." The author, or editor, may prefer to retain (or restore)
articles in symbol lists, figure captions, headings, and titles.
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1.5.2. Unit Modifiers
Technical writing abounds with unit modifiers, that is,
combinations of words that modify another word:
The annular suspension and pointing system for
space experiments is described.
These values identify the beginning of shock wave boundary
layer interaction.
Separated flow wing heating rate values increase sharply
toward a constant value.
Authors and editors often have difficulty deciding when and how to
hyphenate these modifiers. Bernstein (1981) considers hyphens a
necessary evil to be used only to avoid ambiguity. Certainly, unit
mod)fiers need not always be hyphenated and hyphenation does not
always prevent ambiguity.
Before agonizing over hyphenation of these modifiers, consider
changing them to prepositional phrases to clarify their meaning.
Perhaps this change only a few times in a report is sufficient to
clarify the unit modifier when it appears subsequently.
Surely the prepositional phrases in the following sentences are
clearer than the hyphenated unit modifiers:
Unit
modifier
|
The annular suspension-and-pointing system for space
experiments is described.
|
Prep.
phrase
|
The annular system for suspension and pointing of space
experiments is described.
|
Unit
modifier
|
These values identify the beginning of
shock-wave-boundary-layer interaction.
|
Prep.
phrase
|
These values identify the beginning of interaction
between the shock wave and boundary layer.
|
Unit
modifier
|
Separated-flow wing heating-rate values increase sharply
toward a constant value.
|
Prep.
phrase
|
Heating rates on the wing over which the flow is
separated increase sharply toward a constant value.
|
Too many prepositional phrases can make the sentence awkward and
hard to read, as in the last example. The following might be
preferable:
Separated-flow heating rates on the wing increase sharply
toward a constant value.
Probably the best authority on hyphenation of unit modifiers is
the G.P.O. (1984). Unfortunately we sometimes forget rule 6.16:
Where meaning is clear and readability is not aided, it
is not necessary to use a hyphen to form a temporary or made
compound. Restraint should be exercised in forming unnecessary combinations
of words used in normal sequence.
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A unit modifier should not be hyphenated
- When the unit modifier is a predicate adjective: The aircraft
was flight tested.
Note: that an adjective that is hyphenated in the
dictionary is hyphenated as a predicate adjective (IRS 1962): The
method is well-known.
- 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
Of course, there are many instances other than those listed above
when a unit modifier may be hyphenated. See Skillin et al. (1974) and
G.P.O.
15 Back to Top
(1984) for discussions of permissible temporary compound words.
The above guidelines are based on the hyphenation rules proposed by
Murdock (1982). She attempted to eliminate the need for subjective
decisions concerning the clarity of unit modifiers. Unfortunately,
her rules do not always ensure clarity. It seems that authors and
editors must subjectively decide whether or not a unit modifier is
clear and readable without a hyphen.
1.6. Adverbs
Adverbs modify verbs, adjectives, and even other adverbs, but not
nouns or pronouns. Adjectives can modify only nouns and pronouns.
Grammatical errors sometimes occur when an adjective tries to modify
a verb:
Wrong
|
The balance was mounted internal to the model.
|
Correct
|
The balance was internally mounted on the model.
|
Or
|
The balance was mounted inside the model.
|
Note the position of the adverb internally in the above
example. The natural place for a single-word adverb is within the
verb phrase. However, some adverbs can be moved within a sentence to
change emphasis (see section 2.6). Although adverbial words and
phrases can be moved easily within a sentence, they can be misplaced
when their modification is not clear.
See section 2.5.1 for discussion of degree (positive,
comparative, and superlative) of adverbs.
1.6.1. Misplaced Adverbs
Some adverbs such as only, almost, nearly, also, quite, merely,
and actually must be placed as close as possible to the
words that they modify (see the discussion of "only" in Bernstein
1981):
Misplaced
|
The approximation is only valid for u = 0.
|
Correct
|
The approximation is valid only for u = 0.
|
Misplaced
|
The flow had separated nearly over the whole wing.
|
Correct
|
The flow had separated over nearly the whole wing.
|
Misplaced
|
It is only necessary to apply equations (6) to (12) to
compute D.
|
Correct
|
It is necessary to apply only equations (6) to (12) to
compute D.
|
16 Back to Top
1.6.2. Squinting Adverbs
An adverb "squints" when it is not clear whether it modifies the
preceding or the following words:
Squinting
|
Although the operator eventually replaced the
thermocouple, during that test, the temperature
measurements were inconsistent.
|
Either
|
Although during that test, the operator eventually
replaced the thermocouple, the temperature measurements were
inconsistent.
|
Or
|
Although the operator eventually replaced the
thermocouple, the temperature measurements were inconsistent
during that test.
|
1.6.3. Split Infinitives
Despite the fact that split infinitives have usually been
proscribed in formal writing, most, if not all, grammar authorities
recommend splitting an infinitive to avoid ambiguity or awkwardness.
In particular, do not place an adverb before or after an infinitive
if in that position the adverb might appear to modify a word other
than the infinitive:
Split
|
He agreed to immediately recalibrate the surface
pressure instrumentation on the wing.
|
Squinting
|
He agreed immediately to recalibrate the surface
pressure instrumentation on the wing.
|
Awkward
|
He agreed to recalibrate immediately the surface
pressure instrumentation on the wing.
|
Split
|
The flow at
= 0° was the first to completely establish
itself over the wing.
|
Awkward
|
The flow at
= 0° was the first completely to establish
itself over the wing.
|
Squinting
|
The flow at
= 0° was the first to establish itself completely
over the wing.
|
Avoid splitting an infinitive with a phrasal adverb. Such
split infinitives are usually awkward.
1.7. Prepositions
Prepositions are handy little words that connect a phrase to a
sentence and at the same time impart meaning. Prepositional phrases
can function as adjectives, adverbs, or nouns.
When prepositions are used redundantly or unnecessarily, they
should be deleted for the sake of brevity (see section 2.4.1).
17 Back to Top
1.7.1. Prepositional Idioms
Choosing the right preposition to use in a particular construction
is a matter of idiomatic usage, not governed by grammatical rules.
Therefore, when questions arise concerning prepositional idioms,
consult the dictionary, a usage reference (such as Bernstein 1981),
or a list of such idioms (Skillin et al. 1974 and Rowland 1962
contain sections entitled "The Right Preposition"). Some examples of
prepositional idioms follow:
analogous to
|
correlation with
|
attempt (n.) at
|
implicit in
|
attempt (v.) to
|
similar to
|
coincident with
|
theorize about
|
different from
|
variance with
|
1.7.2. Terminal Prepositions
Most authorities agree that ending a sentence with a preposition
is grammatical, although they often recommend avoiding terminal
prepositions because sentences should end with strong words rather
than weak ones (see section 2.6 for positions of emphasis in a
sentence). If deleting a terminal preposition results in an awkward
sentence or changes emphasis in the sentence, nothing has been
gained:
Term. prep.
|
This hypothesis is intuitively difficult to disagree
with.
|
Awkward
|
This is an intuitively difficult hypothesis with which to
disagree.
|
Change emphasis
|
To disagree with this hypothesis is intuitively
difficult.
|
Bernstein (1981) provides an excellent discussion of this topic.
He summarizes by stating, "If by trying to avoid ending a sentence
with a preposition you have seemed to twist words out of their normal
order and have created a pompous-sounding locution, abandon the
effort."
1.7.3. Repeating Prepositions
Prepositions must be repeated in coordinate phrases only when they
are required for clarity or when their omission breaks rules of
parallelism:
Unclear
|
Shock tests were conducted in nitrogen and oxygen.
|
Either
|
Shock tests were conducted in nitrogen and in oxygen.
|
Or
|
Shock tests were conducted in a mixture of oxygen and
nitrogen.
|
Not parallel
|
Tests were conducted not only in nitrogen but also
oxygen.
|
Correct
|
Test were conducted not only in nitrogen but also in
oxygen.
|
Of course, prepositions (and articles) can be repeated for
emphasis.
18 Back to Top
1.8. Conjunctions
Conjunctions are classified as coordinating, joining sentence
elements of equal grammatical rank, and as subordinating, joining
elements of unequal rank.
1.8.1. Coordinating Conjunctions
Coordinating conjunctions join grammatically equal sentence
elements; that is, they join a word to a word, a phrase to a phrase,
or a clause to a clause. They thus provide important opportunities to
use parallelism. See section 2.3 for a discussion of parallel
construction. The three types of coordinating conjunctions are:
Coordinate conjunctions: and, but, or, nor
Correlative conjunctions: either ... or, both ... and, not
only ... but also
Conjunctive adverbs: therefore, however, thus, hence,
otherwise
Coordinate conjunctions
Coordinate conjunctions can join words, phrases, and clauses. The
elements that they join must be equal grammatically. A coordinate
conjunction cannot join a noun and prepositional phrase, for
example:
Wrong
|
Pressures at the bulkhead, the seal, and in the
cove are shown.
|
Correct
|
Pressures at the bulkhead, at the seal, and in the
cove are shown.
|
Nor can a coordinate conjunction join a noun and a clause:
Wrong
|
Notable characteristics of the air duct system are the
acoustic treatment of the ducts and that the
compressor can force flow both ways through the system.
|
Correct
|
Notable characteristics of the air duct system are the
acoustic treatment of the ducts and the ability of
the compressor to force flow both ways through the
system.
|
Correlative conjunctions
Correlative conjunctions are pairs of words that connect parallel
sentence elements.
Each member of the correlative must be followed by the same
part of speech
Wrong
|
The microprocessor provides both radiometer
control functions and formats the data.
|
Correct
|
The microporcessor both controls the radiometer
and formats the data.
|
19 Back to Top
Also it is good practice to keep elements joined by correlatives
strictly parallel:
Poor
|
The subsystem not only measures temperature
but it also provides real-time displays.
|
Better
|
The subsystem not only measures temperature but
also provides real-time displays.
|
Poor
|
This duct serves either as an eductor that
provides an exit to the atmosphere or as an inductor
sucking air into the system.
|
Better
|
This duct serves either as an eductor exiting air
to the atmosphere or as an inductor sucking air into
the system.
|
Conjunctive adverbs
Conjunctive adverbs can be used to join independent clauses only.
In contrast to coordinate conjunctions, conjunctive adverbs have more
modifying character and less connective force.
Clauses joined by conjunctive adverbs must be separated by
a semicolon (or a period):
Coord. conj.
|
The differences were generally about 11 percent,
but larger differences occurred at
= 15°.
|
Conj. adv.
|
The differences were generally about 11 percent;
however, larger differences occurred at
= 15°.
|
1.8.2. Subordinating Conjunctions
Subordinating conjunctions connect dependent clauses to
independent clauses. They are discussed in three categories:
Adverbial conjunctions, which join adverbial clauses to
independent clauses: for example, because, though, after,
where, so that.
Relative pronouns, which are discussed in section 1.3.3.
That, which is used as a function word to introduce
dependent clauses.
Adverbial conjunctions
Subordinating conjunctions that join adverbial clauses to
independent clauses are called adverbial conjunctions. The biggest
problem with these conjunctions is deciding whether the dependent
clause is restrictive or not in order that the sentence can be
properly punctuated (see section 3.5.2).
Some of these conjunctions are often used improperly:
As, since, and while have meanings other than
those involving time, so that care must be taken to ensure that their
meaning is clear.
20 Back to Top
If introduces clauses indicating condition;
whether introduces clauses indicating alternatives:
Wrong
|
Aerodynamic forces were studied on a two-dimensional wing
section to determine if similar trends would be
calculated.
|
Correct
|
Aerodynamic forces were studied on a two-dimensional wing
section to determine whether similar trends would be
calculated.
|
Where refers to place or location. It is often used
incorrectly to replace that, when, or a relative pronoun:
Wrong
|
This formulation is equivalent to the Prandtl-Glauert
transformation, where the body is stretched to correct for
the actual distance.
|
Correct
|
This formulation is equivalent to the Prandtl-Glauert
transformation, by which the body is stretched to correct
for the actual distance.
|
While used in the sense of although or
whereas is becoming accepted, with reservation. Skillin et al.
(1974) approve of using while to mean although so long
as its use "does not defy the sense of at the same time."
Bernstein (1981) describes this usage of while as acceptable,
"but with less universal sanction."
For a better understanding of these or other usage problems,
consult Bernstein (1981) or other usage references.
The subordinating conjunction that
The subordinating conjunction that is defined in the
dictionary as a function word that introduces several types of
dependent clauses, for example, noun clauses:
That the seven-term function does not result in a good
approximation is apparent.
That may sometimes be omitted in noun clauses
(particularly following such verbs as say, think, and
believe), but this omission is not recommended:
Correct
|
The listeners believe the noise might hurt them.
|
Better
|
The listeners believe that the noise might hurt them.
|
Correct
|
The computation is adequate provided it is converged with
respect to collocation order.
|
Better
|
The computation is adequate provided that it is converged
with respect to collocation order.
|
21 Back to Top
When a phrase or clause intervenes between that and
the rest of the dependent clause, that is sometimes
incorrectly repeated:
Wrong
|
He concluded that because checks were made with 128
collocation points and only small differences were found,
that the results shown were converged.
|
Either
|
He concluded that because checks were made with 128
collocation points and only small differences were found,
the results shown were converged.
|
Or
|
Because he made checks with 128 collocation points and
found only small differences, he concluded that the results
shown were converged.
|
1.9. Verbals
The three types of verbals are the gerund (verb ending in
ing used as a noun), the participle (verb used as an
adjective), and the infinitive (verb preceded by to used as an
adverb, adjective, or noun).
1.9.1. Coordinate Gerunds and
Infinitives
Grammar authorities all remind us that a gerund takes a singular
verb:
Substituting the expression into equation (2) yields ...
But these authorities are silent on the number of a verb following
coordinate gerund subjects:
Substituting this expression in equation (2) and
simplifying the result yields . . .
We prefer a singular verb if a series of actions expressed
by coordinate gerunds can be considered a single process.
Likewise, the prepositions should not be repeated before
coordinate gerunds or infinitives that express a process (Rowland
1962):
The following expression results from substituting
equation (1) into equation (2), integrating by parts, and taking
the limit.
The test procedure was to combine the samples in a large vat,
stir the mixture, and then withdraw samples for analysis.
See section 1.7.3 concerning repetition of prepositions in
coordinate phrases.
1.9.2. Idiom Requiring Gerund or
Infinitive
Whether a particular verb should be followed by an infinitive or a
gerund phrase is a matter of idiom, for example,
Correct
|
The display helped the pilot to cope with the increased
work load.
|
Wrong
|
The display aided the pilot to cope with the increased
work load.
|
22 Back to Top
Although the meaning of these two sentences is the same, changing
the verb changes the verbal required by idiom:
Correct
|
The display aided the pilot in coping with the increased
work load.
|
Consult a usage reference (for example, Skillin et al. 1974) to
check for these idioms; the
dictionary also offers an indication of idiomatic usage.
1.9.3. Dangling Verbals
An infinitive, gerund, or participle dangles when the agent of the
action that it expresses is not clear.
Some authorities (IRS 1962; Tichy and Fourdrinier 1988) consider
an introductory gerund or infinitive phrase to dangle when it does
not modify the subject:
When using a nonaligning pitot static tube, the
total velocity component cannot be exactly measured because of the
swirl component.
To predict the thrust and power coefficients of the
propeller, the aerodynamic coefficients must be provided.
Rowland (1962) considers such gerund phrases acceptable because
"they are employed so frequently in technical writing that they may
be said to be idiomatic." The same can be said of introductory
infinitive phrases. These introductory phrases are clearly adverbial
because no one would attribute their action to the subject. Note that
the verbs in the above sentences are in passive voice, so that an
unknown agent can be supplied for the verbals' actions. When the verb
is in active voice, the verbal tends to dangle:
When using a nonaligning pitot probe, the swirl component
precludes exact measurement of total velocity.
Introductory gerund and infinitive phrases do dangle when
they modify a noun in the sentence other than the subject:
Wrong
|
When using a nonaligning pitot static tube, total
velocity cannot be measured exactly by the investigator
because of the swirl component.
|
Correct
|
When using a nonaligning pitot static tube, the
investigator cannot exactly measure total velocity because
of the swirl component.
|
Although Rowland justifies introductory adverbial gerund and
infinitive phrases because they are idiomatic and clearly adverbial,
he does not extend this argument to participles. He condemns dangling
participles as "slovenly English" and "weak constructions that should
be replaced by more robust phrasing." Are dangling participles
slovenly English? Or, like the dangling gerund, are they becoming
idiomatic?
23 Back to Top
Absolute participles
A class of apparently dangling participial phrases that have
become idiomatic are absolute participles (Bernstein 1981). They have
no antecedent and none is intended; that is, they are indefinite, for
example,
The density mode is preferred provided that
optical properties are measured.
Given a variable factor, the fluctuating flow components
can be calculated from equations (31) to (38).
Either the density mode or the pressure mode can be used,
depending on whether supporting optical measurements or
probe measurements are made.
Other idiomatic absolute participles are
generally speaking
|
concerning
|
considering
|
regarding
|
judging
|
beginning
|
Such constructions must be truly absolute, with no antecedent in
the sentence. In the following sentence, what appears to be an
absolute participle is actually dangling:
Dang. partic.
|
An arbitrary factor controls the accuracy of the
calculation depending on pressure fluctuations.
|
Better
|
A variable factor depending on pressure fluctuations
controls the accuracy of the calculation.
|
Technical writing often contains absolute participles that are not
idiomatic, for example,
The arbitrary factor can be assumed to be small and
therefore can be neglected, yielding a first-order
solution.
Such a participle might be justified by arguing that it is an
absolute adjective construction modifying the whole sentence. However
these participles can sometimes be made adverbial:
The arbitrary factor can be assumed to be small and
therefore can be neglected to yield a first-order solution.
Sometimes a participle at the end of a sentence is not absolute,
but actually modifies the subject in a nonrestrictive way:
Nonrestrictive partic.
|
Increasing the leak area caused the boundary layer to
attach, thus decreasing heat transferred to the cove
interior.
|
24 Back to Top
The MLA's Line by Line (Cook 1985) does not object to such
placement of a participle. However, these participles can usually be
changed to a compound predicate:
Compound predicate
|
Increasing the leak area caused the boundary layer to
attach and thus decreased heat transferred to the cove
interior.
|
Do not confuse absolute participles with nominative absolute
constructions, which are perfectly grammatical. Nominative absolutes
have their own subjects and modify the whole sentence:
Dang. partic.
|
Maraging steels are promising for cryogenic service,
having hardness at -320°F of
38Rc.
|
Nom. abs.
|
Maraging steels are promising for cryogenic service,
their hardness at -320°F being
38Rc.
|
Adverbial participles
What appears to be a dangling participle is left when the
preposition by is dropped from an adverbial gerund phrase.
These "adverbial participles" may appear after the verb or at the
beginning of the sentence:
Adverb. partic.
|
The logarithmic derivative is obtained using this
least squares representation.
|
Gerund phrase
|
The logarithmic derivative is obtained by using
this least squares representation.
|
Adverb. partic.
|
Neglecting the dependence of n on Reynolds
number, the results of figure 11 can be used to estimate
n.
|
Gerund phrase
|
By neglecting the dependence of n on
Reynolds number, the results of figure 11 can be used to
estimate n.
|
Adverb. partic.
|
Substituting equation (34) instead of equation
(14), the terms for the fluctuating modes can be
rewritten.
|
Gerund phrase
|
By substituting equation (34) instead of equation
(14), the terms for the fluctuating modes can be
rewritten.
|
Restoring by to these phrases adds very little to the above
sentences. The participles in these sentences clearly modify the
verbs; thus their meaning is clear. But participles are, by
definition, adjectives, so that adverbial participles are not
grammatical. Also there are methods of revising adverbial participles
other than restoring their by. In the following sentences, stronger
constructions replace the participial phrases:
Prep. phrase
|
The logarithmic derivative is obtained from this
least squares representation.
|
25 Back to Top
Prep. phrase
|
With the dependence of n on Reynolds number
neglected, the results of figure 11 can be used to estimate
n.
|
Gerund subject
|
Substituting equation (34) instead of equation
(15) allows the terms for the fluctuating modes to be
rewritten.
|
Dangling participles
When a participle genuinely appears to modify the wrong noun,
truly dangling and thus much more offensive:
Dang. partic.
|
Using a nonaligning pitot probe, the swirl
cormponent precludes exact measurement of total
velocity.
|
Better
|
When a nonaligning pitot tube is used, the swirl
component precludes exact measurement of total velocity.
|
Dang. partic.
|
The shock is essentially normal near the body,
producing subsonic flow.
|
Better
|
Near the body is an essentially normal shock producing
subsonic flow.
|
Dang. partic.
|
Encouraged by these results, a new research effort
was begun.
|
Better
|
Encouraged by these results, we began a new research
effort.
|
Recommendations
When an introductory gerund or infinitive phrase is clearly
adverbial, we consider its use idiomatic and therefore we do not
consider it dangling.
Although no writing authorities now claim that adverbial
participles and nonidiomatic absolute participles are becoming
acceptable in technical writing, such participles are widely used and
well understood. Forbidding their use is perhaps like forbidding the
tide to rise. These participial constructions are certainly not
grammatical, but they are rarely misunderstood.
So long as an adverbial or absolute participle does not
appear to modify the wrong noun, it is acceptable, but not
encouraged.
26
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