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Style Guide Full Text

Below is the full text of the Style Guide for Web pages for the Office of Energy Efficiency and Renewable Energy. The guide features formatting, spelling, punctuation, capitalization, grammar, and language guidelines.

Guidelines are listed alphabetically for easy reference. You may also use the topic index to locate information covered in the guide.

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

A and An

Use a before any acronym or word that begins with a consonant sound. Use an before any acronym or word that begins with a vowel sound. An acronym is pronounced as a word (for example, a HEPA filter); an initialism is pronounced as its letters (for example, an NGO). The first sound of the word or letters indicates whether to use a or an.

Examples:

a light-water reactor: an LWR

a Human Resources Office memo: an HRO memo

a nongovernmental organization: an NGO

Abbreviations

To avoid confusion, spell out an abbreviation in full or define it the first time you use it in the main body of the text. Spell out a technical abbreviation in full in text when you use it without numerals. For example, write "a few centimeters" rather than "a few cm." Otherwise, use the abbreviation consistently.

In brochures, exhibits, and other products for a wide audience, limit abbreviations. If you use many abbreviations in a report, add a list of definitions, glossary, or nomenclature.

Abbreviating Measurement Units

Abbreviate units of measurement. With a few exceptions (such as %, °, $, and ¢), use a space to separate them from numerals.
Examples:
- 900 W/m²
- 43 cm
- 60 Hz
Define measurement units if they might confuse readers. Spell out the term first, and follow that with the abbreviation in parentheses; thereafter, you may use the abbreviation:
Example:
- 250 hectares (ha)
Spell out units of measurement when they're not accompanied by numbers:
Example:
- The new film was several nanometers thicker than the previous one.
Abbreviating Names

When you first use them, spell out the names of professional societies, organizations, processes, technical equipment, and long chemical terms, followed by the abbreviation in parentheses:

Use a small s (no apostrophe) for plurals of most abbreviations (PUCs and CFCs, not PUC's or CFC's). For plurals of units of measurement, omit the s (e.g., 15 cm, 6 m, 5 million Btu, 75 dB, 40 W).
Abbreviating Report Elements

You can abbreviate equation and reference when you use them with numbers, but spell them out at the beginning of a sentence.
Example:
- See Eq. 1-1, Eq. 2-7, and Ref. 10.
- Equation 2-1 shows the relation.

See also acronyms and units of measurement. When writing or editing a journal article, consult the publisher's or professional society's guidelines for abbreviations, if they are available. For abbreviations of journal titles, please see the Web of Science Web site.

Acronyms

An acronym is an abbreviation or initialism that is pronounced as a word:

Examples:

RAM

NASA

OPEC

NORAD

Some common acronyms are no longer capitalized:

Examples:

laser

radar

sonar

Avoid the use of acronyms unless they are used extensively in a Web site or document. In short reports, spell out acronyms that are used fewer than five times. In long reports, spell out acronyms that are used fewer than 10 times. If acronyms are used, spell them out on first use, and put the acronym in parentheses after the full name.

To avoid confusion, try not to use too many acronyms and abbreviations in any sentence or paragraph. Include a glossary or list of acronyms if your publication contains a lot of them.

Active Voice and Passive Voice

Try to write more active-voice sentences than passive-voice sentences. In other words, the subject of most of your sentences should be the "actor" or "agent" (who did it?) rather than the thing "acted upon."

Active voice: We tested the apparatus.
Passive voice: The apparatus was tested by us.

Research shows that active voice helps even highly educated readers absorb information more quickly. Passive voice is no longer considered to be more scholarly or scientific than active voice. Active voice also lends clarity and vigor to technical writing. But sometimes passive voice is appropriate, especially when it's more important to emphasize what was done than who did it. Passive voice can add variety to your writing, too. See also personal pronouns.

Addresses and Phone Numbers

Use U.S. Postal Service abbreviations (such as CO for Colorado and DC for District of Columbia) for states in bibliographies, references, and full addresses (those that include streets or post office boxes):

P.O. Box 123
Denver, CO 80101

In text, when you refer to a state with a city or by itself (for example, "The state energy office is stepping up solar retrofit activities in Massachusetts"), spell out the name of the state in full, except for the District of Columbia (D.C.). See also states and countries.

Use hyphens to separate the 10 digits in phone numbers:

Example:

303-555-1212

Affect and Effect

Affect is usually a verb and effect is usually a noun.

Affect (verb): The new deposition process affected the efficiency of the device.
Effect (noun): We measured the effect of the new process on the efficiency of the device.

These words can be confusing, because affect can sometimes be a noun (when it denotes an emotion), and effect can be a verb (when it means "to bring about").

Air Conditioning

Air conditioning is two words when used as a noun and hyphenated when used as an adjective.

Examples:

Air conditioning is energy-intensive.

The efficiency of the air-conditioning system can be improved.

Appendices

You can include detailed background or technical information in one or more appendices. Large, detailed tables are often placed in an appendix. If you have more than one appendix, title them with letters (Appendix A, B, C, etc.) and name figures and tables so they reflect the title (Figure A-1, Table B-2, etc.). If you have only one appendix, title it "Appendix" rather than "Appendix A."

Assure, Ensure, and Insure

Assure means to guarantee. Ensure means to make certain. Insure means to obtain insurance.

Examples:

The manufacturer assured the group the equipment would work properly.

Ensure the lid is fitted properly before starting the experiment.

The laboratory must insure the new equipment before it can be used.

Because and Since

Because indicates a cause-and-effect relationship. Since indicates a time relationship.

Examples:

Because the equipment malfunctioned, the experiment failed.

Since we began using the new procedures, there have been no more malfunctions.

Bibliography

A bibliography, which is different from a reference list, is a list of works that are related to your subject or publication but not cited, either by author or by number, in text. Alphabetize works in bibliographies according to the last name of the first author. Some bibliographies are titled "For Further Reading." Compile your in-text citations of literature and other sources in a list of references.

British Thermal Units

The abbreviation for British thermal unit is Btu. Btu is used for both singular and plural cases.

Bullets

Bullets are usually printed as solid, centered dots to the left of items in a list. You must have at least two items in a bulleted list.

Make bulleted lists parallel in construction (that is, begin all the items in the list with the same part of speech, such as a verb or a noun).
- Make sure items are either all phrases or all complete sentences.
- Punctuate all items consistently.
Use bulleted lists to highlight important items, draw attention to main points, or help readers find information.
Use numbered or lettered lists instead of bullets if you want to refer to items in a list or procedure elsewhere in the text.
Begin each item with a capital letter; omit ending punctuation for all but the last item, unless all items are complete sentences.

In text, the first level of bullet is indented 0.5 in., and text begins at the 1-in. mark. This level is bulleted with a solid dot. Second-level bullets are open dots, and third-level bullets are em dashes. Each subsequent level of bullet is sequentially indented 0.5 in. In lists of items that are more than one line, each bulleted item is followed by a 6-pt. space.

Capitalization

Capitalizing Proper Nouns

Capitalize proper names. These include the names of government programs, official projects, formal groups, organizations, companies, the Internet, titles when they precede a name (except for the President of the United States, use lowercase in titles that follow the name), specific geographic areas or features, and ethnic groups.
Examples:
- the U.S. Bureau of Mines
- Solarex Corporation
- World Wide Web (the Web), the Internet
- President Carter
- Christine Johnson, president and chief executive officer
- the Southwest
- Lake Powell
- the Colorado River
- African, Asian, Caucasian, Hispanic, or Native Americans
Capitalizing Taxonomic Names

When writing about botanical and zoological divisions, capitalize the names of all divisions higher than species: genera, families, orders, classes, and phyla. Print genera, species, and varieties in italics.
Examples:
- Clostridium thermocellum
- Escherichia coli
After you first mention them (and spell them out), you can abbreviate most generic names followed by species names.
Examples:
- C. thermocellum
- E. coli
Capitalizing Table Titles, Headings, and Captions

Capitalize the main words of table titles and most headings and subheadings, including the second word in a hyphenated term (e.g., PV Program Five-Year Plan). Do not capitalize articles (e.g., a, an, and the) unless they begin the title or heading; conjunctions (e.g., and, or, nor, and but); or prepositions (e.g., for, of, and to). When to is used in a table title or heading, it is capitalized as an infinitive and lowercase as a preposition.
Examples:
- Table 1. Number and Frequency of Defects in Six Samples
- (May–June 1998)
- Testing the 7.6-m Blades (subhead)
- Results for E. coli (subhead)
- Development of Method To Detect Anomalies (subhead)
Capitalize only the first word and proper nouns in figure captions.
Example:
- Figure 1. Results for the electrochromic window
Follow the style recommended by your professional society or journal publisher regarding the word figure and its abbreviation (Fig.) when you prepare a paper or an article for submission to a conference or journal. Many societies and publishers recommend lowercasing everything but the first word and proper nouns in all table titles, subheads, and captions.
Capitalizing States and Titles

Capitalize the names of states, but capitalize state only when it appears with the entire official name:
Examples:
- the State of Colorado; Washington State
Capitalize titles when they precede the person's name. Lowercase titles and names of groups when they follow the name:
Examples:
- Chief Operating Officer Mark Wilson
- Mary Jones, the president of the company
- John Smith, the chair of the committee
Capitalizing Trade Names

Capitalize trade or brand names, and include a trademark, copyright, or other symbol only when it's part of the official name. Include the symbol the first time you use the trade name in body text; thereafter, you may omit the symbol:
Examples:
- Pyrex®
- Kleenex®
- ENERGY STAR^®

Refer to the company's literature or stationery if you're not sure. See also the online database of current trademarks.

Captions

All substantive photos should be accompanied by a caption. Begin figure and photo captions with a capitalized word and use lowercase thereafter, except for proper nouns and capitalized abbreviations. Unless you add a subcaption, you don't need a period at the end of a caption.

Chemical Terms

Do not use a hyphen in most chemical expressions, even when the terms are used as modifiers.

Examples:

carbon dioxide levels

hydrogen ion activity

Use a hyphen after prefixes when that's the standard for certain chemical formulas.

Examples:

L(+)-2, 3-butanediol

trans -glycol

Use a hyphen to indicate mixtures or combinations.

Example:

hexane-benzene

Colons

Colons formally introduce a list or series, a question, or an amplification. Colons often separate the parts of a ratio.

Examples:

We test three types of collectors: flat plates, evacuated tubes, and parabolic troughs.

We added enough water to obtain a 3:1 dilution.

But commas, not colons, usually follow words such as that is, namely, or such as. You don't need a colon after a verb or preposition that precedes or introduces a list (includes, to, with, between, etc.). Use a colon when a noun (such as the following) introduces a list in text.

Commas

When To Use Commas

Use a comma to separate items in a series, including the next-to-last word in the series:
Example:
- We develop solar thermal, wind, biomass, and photovoltaic energy technologies.
Use a comma to separate the parts of a compound sentence linked by a coordinating conjunction (such as and, but, or, or nor) when each part has its own subject and verb (unless they're very short):
Example:
- I laughed at the unintentional joke, but she frowned.
Use commas to set off nonessential or nonrestrictive (parenthetical) words, phrases, and clauses from the rest of the sentence. In other words, the commas signal that the information between them is something extra and not essential to the meaning of the sentence
Example:
- The subsystem, which takes a day to install, will be delivered in two weeks.
Use commas to enclose the name of a state when it follows a city and a year when it follows the month and day.
Examples:
- The test systems in Gardner, Massachusetts, are performing well.
- The next test sites will be in Golden, Colorado, and Chapel Hill, North Carolina.
- On April 11, 1998, the committee members completed five of the six objectives.
Place commas (and periods) inside quotation marks; place semicolons, question marks, dashes, and exclamation points outside quotation marks unless they're part of the quotation.
Examples:
- "The results are in," he said.
- "Can you hear me?" she asked.
- Did he really say "I don't believe you"?
When Not To Use Commas

Do not use a comma to separate compound subjects or compound verbs.
Examples:
- Theorists and nonspecialists alike agree on the importance of the discovery. (There is no comma between the two parts of this compound subject.)
- The researchers rolled out the thin metal sheet and formed it into coils. (There is no comma between the two parts of this compound verb.)
Do not use commas to set off words or phrases that are restrictive, that is, essential to the meaning of a sentence.
Examples:
- Only the sensors that were attached to the outer edge failed. (The words are essential to the meaning of the sentence.)
- The system will work efficiently only if it includes storage. (The words are essential to the meaning.)

Common Errors in English Usage

Confused about when to use amount and when to use number? The Common Errors in English Web site can help.

Compose and Comprise

Composed of is correct; comprised of is incorrect.

Examples:

The United States is composed of 50 states.

The parts constitute the whole.

The whole comprises its parts.

The department comprises four groups; each group is composed of five to seven scientists, technicians, and support staff.

Compound Words, Unit Modifiers, and Hyphens

Verb Phrases: Verb, Noun, and Adjective Forms

Verb phrases that contain an adverb (build up, set up, start up, break down ) are usually written as two words. The noun and adjective forms of these words are either one word (no hyphen) or a hyphenated form of the words. However, there are exceptions. Refer to the dictionary for the correct spelling.
Examples:
- We observed the slow buildup of biofouling on the blades.
- We helped with the setup.
- The start-up costs were higher than we estimated.
- I think I'm having another breakdown.
Compound Words Containing Prefixes and Suffixes

You don't need a hyphen between many prefixes and suffixes and the root words, unless the root word is a proper noun:

multidimensional
multiyear
reevaluated
threefold, hundredfold
(also 100-fold)

prescreening
postdoctoral
retroactive
nonspecialist
subassembly

These prefixes usually require a hyphen: ex -, self -, quasi -.
Unit Modifiers with and without Hyphens

Use a hyphen to indicate that words have been combined into a unit modifier, which is a descriptive expression composed of two or more words that form one new meaning. For example, in the term flat-plate collector, flat-plate is the unit modifier. Although there is a tendency in modern writing to eliminate hyphens, they help prevent ambiguity and confusion. Here are some examples of unit modifiers that usually include hyphens:
- low-level radiation
- last-minute addition
- band-gap energies
- fatigue-induced wear
- five-year plan
- nine-story building.
To see how adding the hyphen can prevent confusion, consider these examples:
- The scientists tested a new defect causing gas.
- The scientists tested a new defect-causing gas.
In the first example, the scientists might seem to have been testing a defect; in the second example, it's clear that they have tested a gas.

You don't need a hyphen in common unit modifiers that are not ambiguous or confusing.
- high school students
- solar radiation resource
- solar thermal electric systems
Don't use a hyphen when both words of a unit modifier are capitalized:
- Bronze Age tools
- Vietnam Era veterans
- Biofuels Program objectives
Leave out the hyphens if you rewrite a sentence so the words in the unit modifier come after the noun they describe.
Examples:
- We purchased state-of-the-art lab equipment.
- We purchased lab equipment that reflects the state of the art.
- They made some last-minute adjustments.
- They made some adjustments at the last minute.
Don't use a hyphen with a unit modifier containing an adverb ending in -ly:
Examples:
- frequently missed deadlines
- heavily skewed results
When you use numbers in unit modifiers, retain all the necessary hyphens.
Examples:
- 2-in.-diameter tubes
- 13-cm-wide substrate
Or rewrite the sentence to omit the hyphens.
Examples:
- tubes that are 2 in. in diameter
- a substrate that is 13 cm wide.
Use a hyphen between prefixes and proper nouns (but not common nouns) or dates, whether they're used as nouns or modifiers:
Examples:
- non-EERE
- mid-1990s
Use two hyphens when adding a prefix to a word that already contains a prefix, even when there is no hyphen after the prefix in the original word:
Examples:
- non-self-limiting
- multiple-band-gap

Comprise and Compose

See compose and comprise.

Criterion

Criterion is a singular noun (one criterion) and criteria is the plural (two or more criteria).

Dashes

Use dashes (often called long dashes or em dashes) to enclose and set off parenthetical (nonessential but often illustrative) information in a sentence. Also use dashes to set off a list of items separated by commas. Do not add spaces around the dash.

Example:

The polymer components of the cell walls—cellulose, hemicellulose, and lignin—provide the feedstocks for these chemicals.

Use an em dash to signal that an important point is going to be made or that a change in the construction of the sentence follows.

Examples:

The presentation concluded with a discussion of the two project factors that concern contractors the most—cost and time.

The major omission in the project assessment was the delay caused by the circuit failures—everyone knew about it but no one mentioned it to the reviewers.

You can usually use commas, colons, and semicolons in place of dashes, but dashes add special emphasis.

Use shorter dashes known as en dashes (rather than a hyphen or em dash) to indicate a range or to substitute for the word to.

Examples:

25–45 cm²

2–5 runs per hour

See sections 3.1–3.6.

Do not use an en dash (or hyphen) to mean and; the word between is followed by the word and (not to).

Example:

between 25 and 30.

Data in Tables

Place a zero to the left of the decimal in any number less than 1 in text and tables (e.g., 0.5, 0.039). Align columns of data vertically on the decimals. When the units of measurement for the data are different, alignment is not necessary (but be sure to specify the units).

Dates

Use common month abbreviations when a full date is provided. Use cardinal numbers for the day.

Examples:

Jan. 1, 2010

May 6, 1990

Datum

Data is the plural of datum.

Degree Symbol

Print the degree symbol right next to the symbol for the temperature scale.

Examples:

36ºC

85ºF

Repeat the degree symbol in ranges.

Example:

32º-36ºC

Express kelvins as K rather than as ºK; leave a space before the K.

Example:

85 K

Dollars

Express thousands of dollars using a comma.

Example:

$5,000

Express millions and billions of dollars this way.

Examples:

$3 million

$1.2 billion

In technical reports and papers, use a dollar sign to express costs less than $1.

Examples:

$0.25

$0.06 per kilowatt-hour

Effect and Affect

See affect and effect.

Ellipses

When you want to leave out part of text material you are quoting, use ellipsis marks (three dots with a space on each side) to indicate the omission.

Example:

A participle is "a word having the characteristics of both verb and adjective ... [that] shows such verbal features as tense and voice. ..."

If the words before the ellipses form a grammatically correct sentence, put a period at the end of the sentence and follow it by ellipses. In most cases, however, you don't have to use ellipses at the beginning or end of quotes, just within them. When you add a word or words to the quote, to make it clear, enclose the added word or words in brackets to show that it is not part of the original quotation.

When you quote whole paragraphs but omit text between any two of them, center three asterisks, with spaces between them (* * *), between the paragraphs quoted. See also quotation marks.

ENERGY STAR

ENERGY STAR is always in capitals. If the first instance of ENERGY STAR is in the content, use ENERGY STAR^®. If the first instance is in a header, use ENERGY STAR® without the superscript. In both cases, use ENERGY STAR thereafter. There is no space between the ® and ENERGY STAR.

Ensure, Insure, and Assure

See assure, ensure, and insure.

Equations

Make sure that all the terms in your equations are defined and used consistently both in the text and in subsequent equations, figures, and tables.

Example:

The conductive heat flow equation is:
dQ/dt = AKdT/dx,

where
dQ/dt = the time rate of heat transfer
A = the area of an end contact
K = the thermal conductivity
dT/dx = the thermal gradient.

Etc.

Because it's vague, please use etc. (et cetera) sparingly. Don't add it to the end of a list beginning with "for example," or the abbreviation e.g., because each word in your list is an example of your subject or topic, but "etc." is not, so you don't need it.

Executive Summary

If you include a summary in a report, place it before the contents page. If your report is brief, a summary is not usually necessary. If your report is long, or if you think some readers will want one, you can include an executive summary. Executive summaries of very long reports can be published separately.

Figures

Figures can include line drawings, graphs, charts, diagrams, schematics, flow charts, illustrations, and photographs. Use an Arial font and consistent line weight in your figures. Be sure that computer-generated figures are clear and readable so they can be reproduced easily.

Use 10-pt. Arial bold for captions; capitalize only the first word and proper nouns. Number figures in a simple sequence (e.g., Figure 1, Figure 2). In long reports, papers, or book chapters, you may include section or chapter numbers in the figure numbers (e.g., Figure 1-1, Figure 1-2, Figure 2-1, and so on).

Make sure the data in your figures correspond to the data in your text and tables. The caption is placed under the illustration (see also captions).

Line drawing showing how photovoltaic cells make electricity that can be used and stored from sunlight.

Figure 2-1. Photovoltaic cells use sunlight to provide energy to a home

First-Person Pronouns

First person pronouns should generally be avoided. However, some scientific and technical associations (such as the American Institute of Physics) ask technical writers to use first-person pronouns when it is appropriate. First-person pronouns include I, we, my, our, me, and us; second-person pronouns are you and your; and third-person pronouns include he, him, her, his, hers, they, their, and them. See also personal pronouns.

Fiscal Year

Spell out fiscal year (e.g., Fiscal Year 2006) the first time you use it; after that, you can abbreviate it using two capitals followed by a space before the full year (e.g., FY 2001). FY01 may be used to save space in charts and graphs. For Web body text, spell out fiscal year on each use.

Foreword

The foreword to a book or formal report contains introductory remarks written, and usually signed, by someone other than the author or authors. Brief introductory remarks written by authors are contained in a preface.

Fractions

Use words instead of numerals for simple fractions in text.

Examples:

a third of the way

one-fifth its actual size

three-fourths of the participants

Write out complex fractions with numerals separated by a solidus.

Examples:

1/64

23/32

5-1/2 days afterward

2-1/2 times greater

Display complex, built-up fractions by centering them vertically between two parts of a paragraph.

Place a zero to the left of the decimal in fractions less than 1.

Examples:

0.125

0.006

Geographic Regions

Capitalize regions of the United States when they appear by themselves.

Examples:

the East, the West, the North, and the South

the Southeast, the Northeast, the Southwest, the Pacific Northwest

the Midwest, the East Coast, the West Coast, the Gulf Coast

Don't capitalize words that merely describe general areas in the country or areas of a state.

Examples:

the eastern United States

southwestern Nebraska

northern New Mexico

the midwestern states

Glossaries and Nomenclatures

If you use many mathematical or Greek symbols or technical terms in your report or paper, consider defining them in a glossary or nomenclature. Arrange the list alphabetically, and group Greek letters and definitions alphabetically in a separate list. Nomenclatures are usually in the front of a report, before the contents page. Glossaries usually go in the back, before the references.

Hybrid Electric Vehicle

This phrase contains no hyphens.

Hyphens

See compound words, unit modifiers, and hyphens.

Initialisms

An initialism is similar to an acronym, but it is pronounced by its letters.

Examples:

American Society for Testing and Materials (ASTM)

National Fire Protection Association (NFPA)

public utility commissions (PUCs)

chemical vapor deposition (CVD)

compact vacuum insulation (CVI)

chlorofluorocarbons (CFCs)

Use a small s (no apostrophe) for plurals of most initialisms (e.g., PUCs and CFCs, not PUC's or CFC's).

Avoid the use of initialisms unless they are used extensively in a document. In short reports, spell out initialisms that are used fewer than five times. In long reports, spell out initialisms that are used fewer than 10 times. If initialisms are used, spell them out on first use, and put the initialism in parentheses after the full name.

To avoid confusion, try not to use too many in any sentence or paragraph. Include a glossary or list of acronyms if your publication contains a lot of them.

Insure, Assure, and Ensure

See assure, ensure, and insure.

Italics

Using Italics for Emphasis

Use italics (sparingly) to emphasize a word or phrase or bring attention to it.
Example:
- Never operate this equipment when it has a yellow danger tag.
Using Italics for Foreign Words and Phrases

Italicize such foreign words and phrases as in situ, in vivo, and inter alia; however, if the word or phrase is commonly used in your field, you may omit the italics.
Using Italics for Hyphenated Prefixes

Italicize hyphenated prefixes (such as cis-, trans-, o-, m-, and p-) to chemical formulas.
Examples:
- trans -1, 2-dibenzoylethylene
- trans -glycol
Using Italics to Cite Published Documents

Use italics in references, footnotes, and bibliographies for book titles and the names of journals, newspapers, and magazines.
Examples:
- Gone with the Wind
- Applied Physics Letters
- The Denver Post
- Science
But print the titles of journal and magazine articles in regular Roman type within quotation marks.
Example:
- "Solar Chimney Theory: Basic Precepts"
Using Italics in Taxonomic Names

Unless you're discussing a genus in a general way, use italics to refer to specific genera, species, and varieties.
Examples:
- Clostridium thermocellum
- C. thermocellum
Using Italics to Refer to Words as Words

Italicize a word or phrase (or enclose it in quotation marks) when you're referring to it as a word or as a phrase.
Examples:
- The word footnote is often used in place of reference.
- He wrote ambiguous, but I think he meant ambivalent.

It's and Its

Even though it's has an apostrophe, it isn't a possessive pronoun. It's is a contraction, a short form of two words, like isn't. It's always means it is. Its is the possessive form of it. Like his, hers, and ours, the possessive its never needs an apostrophe.

Example:

It's a shame that the company lost its biggest investor.

Laboratory and Lab

Only capitalize laboratory or lab when used with a laboratory's full name. Lowercase in all other references.

Example:

The National Renewable Energy Laboratory is a U.S. Department of Energy national laboratory. The laboratory is known for its research and development in renewable energy and energy efficiency.

Lists

You can use bulleted or numbered lists. Here's an example of a numbered list:

Include at least two items in a bulleted or numbered list.
Use numbered lists for procedural steps and for items referred to elsewhere in text (for example, "as described in Step 2").
Use parallel construction in lists; that is, make all the listed items similar. Use sentences or phrases throughout, and begin each item with a verb or a noun consistently.
1. use lowercase letters to mark subordinate items in your list.
2. make sure you have at least two subordinate items under each main item.
3. indent them like this.
Use punctuation in lists when the items are complete sentences; otherwise, place a period after the last item only.

You can also list a few items or procedures in paragraph format and number them (1) one, (2) two, (3) three, etc. See bullets for more formatting information.

Mathematical Symbols

Leave a space on either side of mathematical symbols used as operation signs.

Examples:

T_in - T_amb

ºC × 1.8

The solidus (a/b) or division sign is an exception. Do not leave a space between numerals and the symbols for degrees, dollars (or cents), and percent (32º, $100, 17%). (Leave a space between numerals and symbols of measurement such as cm and Å, however.) Do not leave a space between symbols such as >, <, and the numeral unless they are the operation signs in an equation.

Measurement Units

See units of measurement.

Memorandum

The plural of memorandum can be either memoranda or memorandums.

Metric Conversions

For quick online conversions of English units of measurement to metric units, see the Digital Dutch Unit Converter or the Internet French Property Measuring Units Converter Table.

Metric System

See SI (Metric) System.

Misplaced Modifiers

Modifiers in the wrong place can make a sentence confusing.

Example:

After identifying the correct material, the test procedure took about 5 minutes.

In this example, it isn't clear who or what identified the correct material. This might be better: After identifying the correct material, we conducted the five-minute test procedure.

Example:

After being lost under a pile of old reports for 5 years, she finally found the manuscript.

What, or who, was lost—the manuscript, the woman, or the reader? Try to keep modifiers as close as possible to the people and things they describe. Strunk and White, authors of The Elements of Style, say this: "Modifiers should come, if possible, next to the word they modify." This is especially true for sentences containing introductory prepositional phrases or clauses followed by a comma.

Months and Years

Spell out the names of months in text. However, May, June, and July are usually spelled out in full. Abbreviate other months to the first three letters, except for Sept. Month names may not be abbreviated in tables and figures. Omit commas when the month and year appear together (October 2001). When you include the day, use this format: Oct. 1, 2001.

Multiplication Symbols

Be as consistent as possible in using multiplication symbols; as appropriate, choose one symbol (× or ·) or omit the symbol and use proximity or parentheses: ab, (ab) (cd), etc.

Nomenclatures

See glossaries.

Nonrestrictive Phrases and Clauses

A nonrestrictive phrase or clause is one that adds information but is not essential to the meaning of the sentence.

Examples:

The principal investigator, who has studied thin films for 10 years, will chair the panel discussion.

The passive solar features, which were suggested by EERE staff, reduced the agency's energy bills by 30%.

Nonrestrictive or nonessential phrases and clauses are enclosed between two commas when the phrase or clause is within a sentence, and they usually begin with the pronoun which rather than that. See also restrictive phrases and clauses and which and that.

Non-SI (English) Units of Measurement

Use non-SI (Systeme International d'Unites) or nonmetric units of measurement (English or Imperial units) instead of metric units only when they are the industry standard. Otherwise, state metric units first, followed by English equivalents in parentheses.

Example:

38.1 m (125 ft)

Nouns

Technical writing can get bogged down when long sentences become overcrowded with passive voice and certain long nouns (e.g., determination, completion, accomplishment, achievement, measurement, conversion, characterization, combination). To give your writing more flow and vigor, try changing some of the nouns (especially those ending in -tion and -ment) to verbs (e.g., determine, complete, accomplish, achieve, measure, convert, characterize, combine) and other parts of speech. Doing this will move your readers along more quickly and make it easier for them to understand your text. In these examples, we changed some of the nouns in the first sentences to verbs and other parts of speech.

Examples:

Contraction of the tree stems occurred with rapidity.
The tree stems contracted rapidly.

The frequent result of this process is the combination of the molecules.
This process frequently causes the molecules to combine.

The application of fertilizer has the result of stimulation of the yield.
Applying fertilizer stimulates the yield.

Which sentences were easiest to read and understand? When you change some nouns to verbs and delete unnecessary words, your writing can be more clear and vigorous.

Noun Strings

Try not to string too many noun modifiers together in a sentence. An "agency personnel communications interface display" could also be called a "display of the communications of the agency's personnel." Better yet, it could just be called the "staff bulletin board."

Numbers

Units of Measurement and Mathematical Expressions

Use numerals with units of measurement and time.
Examples:
- 2-1/2 hours
- 4.5 months
- 36 cm
- 87 years
- 6 liters
- 25 kW
With units of time, you can spell out numbers less than 10 if you do so consistently (this applies mainly to outreach products rather than technical reports and papers).
Examples:
- five-year plan
- two-hour test
- three-week turnaround
Use numerals to imply arithmetical values or manipulation.
Examples:
- a factor of 3
- multiplied by 2
- a ratio of 4:5
- values of 1 and 48
Express measurement errors as: 6 nm ± 0.2 nm.

Leave a space between the number and the unit of measurement (0.2 nm) and put spaces around the operation sign; when the measurement error appears by itself, omit the space between the sign and the number.
Example:
- The measurement error is ±0.2 nm.
Aligning Numbers

Align numbers that share a common unit of measurement on the decimals in columns of tables. Put a zero before the decimal in numbers smaller than one.
Examples:
- 0.8
- 2.45
- 187.362
If all the numbers in a column do not share the same unit of measurement, you may center the numbers in the column and specify the unit of measurement.
Fractions and Decimals

You can spell out and hyphenate simple fractions (this is preferred in text) or express them, like more complex fractions, in numerals with a solidus.
Examples:
- one-fifth or 1/5
- 1/64 (but not 1/64th)
Use a hyphen to separate the integral and fractional parts of a mixed number, or convert the fraction to a decimal.
Examples:
- 2-1/2 cm in diameter
- 2.5-cm-diameter solar cell
For numbers of 1 million or more, use the numeral (and a decimal, if necessary) and the words million, billion, etc.
Examples:
- 1.1 million households
- 3.5 billion people
- $2.5 million in funding
Precision and Numbers

Measurement uncertainty analysis calls for precision in measurements to a significant digit to the right of a decimal point, such as two or three digits (hundredths or thousandths). If you're not absolutely sure, check with an expert before changing the number of digits to the right of the decimal, or rounding the numbers. See also standard errors.
Punctuating Numbers

Use a comma to separate groups of three digits in numbers.
Examples:
- 5,182
- 113,728
- 2,225,000
Ranges of Numbers

To show ranges, use an en dash (which is a little shorter than an em or long dash) or the word to when you use of or from before the range. To express a range between some number and another number, always use the word and (not to) with the word between.
Examples:
- 15%-25%
- from 32º to 40ºC
- 6-12 cm
- from 66 to 80 V
- 10-20 m²
- between 8 and 12 m (not "between 8 to 12 m")
Note that some symbols, like º and %, are repeated in a range.
Scientific Notation

Express multiples of SI (metric) units in powers of 10 with the appropriate prefixes and technical abbreviations.
Examples:
- mm (millimeters, 10^-3 m)
- MJ (megajoules, 10⁶ J)
Use standard scientific notation to express very small and very large numbers.
Examples:
- 2.5 × 10^-3
- 3.56 × 10⁶
Avoid using M to mean thousands and MM to mean millions; use a capital M for "mega," or millions, as in MW for megawatts.
Spelling Out Numbers

Except with units of measurement and time, spell out numbers less than 10.
Examples:
- eight experimental runs
- three species of yeast
Spell out all numbers at the beginning of a sentence.
Examples:
- Fifteen trials later, the results were the same.
- Thirty-five participants attended the seminar.
When a sentence contains one or more numbers greater than nine that are related to a smaller number, use numerals for all of them.
Examples:
- The results were the same in 3, 12, and 18 trials.
- The contractor tested 8 devices in May, 12 in June, and 9 in July.
Spell out the first of two adjacent numbers unless the first one requires three or more words.
Examples:
- ten 5-kW arrays
- thirty-two 4-cm² devices
- 135 16-cm collectors

Over and Under

In cases involving quantity, use more than rather than over and fewer than or less than rather than under.

Example:

More than 500 people attended the conference, about 100 fewer than last year.

Parallelism

Use parallel construction in sentences as well as in lists. Express all similar sentence elements (subjects, verbs, verbals, objects) in a similar way.

Not Parallel Structure:

The lever was moved completely forward, going slightly to the right, and then it went backward halfway in order to complete the procedure.
We are not only responsible to our chief customer but also the taxpayers.

Parallel Structure:

To complete the procedure, push the lever all the way forward, slide it slightly to the right, and then pull it halfway back.
We are responsible not only to our chief customer but also to the taxpayers.

Parentheses

Use parentheses as appropriate for explanatory material in text, and as shown in the examples that follow.

Parentheses in Equations

Use parentheses, brackets, and braces in this sequence (which may be repeated as needed):
{[( )]}
Parentheses with Measurements

Use parentheses around English measurements that follow SI (metric) measurements.
Example:
- 3.1 m/s (7 mph)
Parentheses in Citations

When you use parentheses in text, such as for author-date references or for parenthetical (added) information, place a comma after the parentheses rather than before them.
Example:
- In earlier research (Jones 1989), we showed how quantities of lipids could be increased by this method.

Passive Voice and Active Voice

See active voice and passive voice.

Percent, %, and Percentage

Use the symbol % with numerals; use the word percent when you spell out numbers at the beginning of a sentence. To determine whether percent or % is singular or plural, look at the noun following it. If the next noun is a plural, use a plural verb; if it's singular, use a singular verb.

Examples:

The maximum glucose yield was 60%.

Six percent of the pipes were rusty.

More than 10% of that amount was allocated to planning.

When there is no number, use the word percentage, unless people in your field use a different terminology, such as percent difference.

Example:

This table shows the percentages of government buildings having solar roofs, by state.

Periods

Periods are used in some abbreviations (e.g., i.e., a.m., p.m.) and not in others (ac, dc, rpm). Most acronyms do not have periods. When you end a sentence with etc. (although this is seldom necessary) or another abbreviation that already includes a period, do not add another one.

Example:

This paper describes the program's purpose, objectives, schedule of deliverables, etc.

(Better: This paper describes the program's purpose, objectives, and schedule of deliverables.)

Personal Pronouns

Many people have been taught not to use personal pronouns (I, we, they) in technical and scientific writing, because this kind of writing is supposed to be formal and objective. However, most modern technical style guides (such as the AIP Style Manual) recommend using personal pronouns in papers and reports. Personal pronouns prevent confusion by clearly and concisely showing who performed an experiment or procedure.

Examples:

We tested several hundred isolates that were able to ferment glucose.

We deposited a thin film of doped cadmium on the substrate.

Which of these two sentences is easier to read and understand quickly?

It was determined that the workshop was a success.
We agreed that the workshop was a success.

Phenomenon

Phenomenon is singular, and phenomena is plural.

Phone Numbers and Addresses

See addresses and phone numbers.

Photographs

When you use an image, credit the photographer or other source as a courtesy or for legal purposes. Provide a caption when necessary. See captions.

Prefixes

See compound words, unit modifiers, and hyphens and scientific notation.

Pressure

Use the standard SI unit for pressure or stress, which is the pascal (Pa) or the bar. Non-SI units include psi (pounds per square inch), millimeters of mercury, torr, and atmospheres, and they are still in relatively widespread use.

Principal and Principle

Principal often means chief or main, such as the principal investigator in a research project or the principal of a high school. Principle often refers to a belief, value, or rule.

Quotation Marks

Use quotation marks for direct quotes and the titles of articles, papers, and reports. In print, use "curly" or "fancy" quotation marks. Place quotation marks outside periods and commas but inside colons and semicolons.

Examples:

"Let's meet again in 6 months," the chairman said, "to discuss our progress."

She presented a paper titled "Materials Research in Silvered Polymer Reflectors."

Use single quotation marks to indicate a quotation within material that is already enclosed in double quotation marks.

Example:

"Explain what you mean by 'confidence,'" she said.

When quotations are longer than two or three lines of text, begin them on the next line and indent them on each side (block quotations). You do not need quotation marks around block quotations, and you can use standard double quotation marks for quotes within block quotations. In in-text quotations, place reference numbers, superscripts, and author-date citations outside quotation marks (but before the final punctuation of a sentence). Place them after the final punctuation of the last sentence in a block quotation.

Ratios

In general, use a colon to indicate a ratio.

Example:

We prepared a 3:1 dilution.

However, some industries (such as the American automotive industry) use a solidus to express a ratio.

Example:

The engine is designed to have an optimum air/fuel ratio.

Restrictive Phrases and Clauses

Do not use commas around restrictive phrases and clauses. They are essential to the meaning of the sentence, in contrast to nonrestrictive phrases and clauses, which simply add information that is not essential.

Restrictive clause (begins with that) containing essential information:
This is the house that Jack built.
Nonrestrictive clause (begins with which) containing additional information:
This house, which Jack built, needs repairs.

Scientific Notation

Standard scientific notation represents a number as a factor multiplied by a power of 10; 3,560,000 is expressed as 3.56 × 10⁶. This is useful for very large and very small numbers, especially in non-SI units. You can also use certain standard prefixes, many of which are listed here with their abbreviations.

10²⁴	yotta	Y
10²¹	zetta	Z
10¹⁸	exa	E
10¹⁵	peta	P
10¹²	tera	T
10⁹	giga	G
10⁶	mega	M
10³	kilo	k
10²	hecto	h
10¹	deka	da
10^-1	deci	d
10^-2	centi	c
10^-3	milli	m
10^-6	micro	µ
10^-9	nano	n
10^-12	pico	p
10^-15	femto	f
10^-18	atto	a
10^-21	zepto	z
10^-24	yocto	y

We recommend choosing a prefix that permits the numerical value to fall between 0.1 and 1,000 (62 kW rather than 62,000 W).

Semicolons

Semicolons indicate a stronger or more important break in the flow of words than the break indicated by a comma. Use a semicolon in compound sentences that are NOT linked by a conjunction (such as and, but, or, nor, yet). Place a semicolon before conjunctive adverbs (such as however, hence, therefore, nevertheless, consequently) in most complex sentences containing two or more clauses. When a sentence contains items in a series, you may use a semicolon between the items if one or more of the items contains commas.

Using Semicolons in Compound Sentences without Conjunctions

When clauses in a sentence are closely related in meaning, a semicolon is an appropriate dividing punctuation mark. Note that the words and, but, or, and nor do not follow semicolons.
Example:
- It was difficult to reproduce the experiment; the material Smith and Jones used was not widely available. Of the 13 samples, only one did not degrade; others deteriorated an average of 8%.
Using Semicolons with Conjunctive Adverbs

Yet and so are usually preceded by commas in a complex sentence. But use a semicolon before such conjunctive adverbs as then, however, thus, therefore, hence, accordingly, moreover, nevertheless, consequently, besides, indeed, and subsequently; place a comma after the adverb.
Examples:
- The contractor's representative was out, so I left a message.
- We used the Schartz-Metterklume method in the experiment; however, the problems with this method are well known.
- Energy requirements are often expressed in quads, or quadrillion Btu; therefore, this report describes the number of quads supplied annually by each option.
Use a semicolon before i.e. ("that is") and e.g. ("for example") and a comma after them when a clause (with a subject and verb) follows them; use a comma when a phrase or list follows.
Using Semicolons in a Series

When items in a series contain internal punctuation (e.g., commas) or are very long, you can separate them with semicolons. In those cases, a conjunction can follow the last semicolon.
Examples:
- The contaminants in the sample were TCE, 150 ppb; toluene, 220 ppb; and benzene, 265 ppb.
- Promising new technologies demonstrated at the exposition included advanced wind turbines; polycrystalline, thick-film, and thin-film solar cells; fast-growing energy crops; and fuel cells.
- The vendor assured us that the replacement parts, which were essential in this installation, were on order; that the parts would be delivered as soon as they arrived; and that the delay in shipment was unavoidable.

SI (Metric) System

EERE follows national policies and those of scientific societies by using the SI (Systeme International d'Unites; International System of Units) or metric system in expressing technical measurements. English units may follow metric ones or may be used alone in special cases, when that is appropriate for a publication's audience. See also the National Institute of Standards and Technology.

Since and Because

See because and since.

Slash (Solidus)

The solidus (or slash, slant, shilling mark, or virgule) is a versatile symbol that has mathematical as well as textual functions.

Using a Solidus in Fractions

Use a solidus to express a quotient in text when you do not need to use a displayed equation.
Example:
- These structures yield photoluminescence lifetimes that are related to bulk lifetime by the expression .
Use a solidus in superscript and subscript fractions.
Example:
- x^1/2
Using a Solidus in Text

In text, use a solidus to indicate some junctions, interfaces, and components.
Examples:
- gas-liquid interface
- 1-butyl acetate/acetic acid/water (3:1:1)
With abbreviated units of measurement, the solidus stands for per.
Examples:
- 2 g/cm²
- 355 W/m²
But spell out per when you spell out the units of measurement.
Examples:
- several cubic meters per second
- a few cents per kilowatt-hour

Sources

Include the sources of all figures and tables that were originally published by others, especially those outside EERE. If figures or tables come from a copyrighted publication, you may need permission to reproduce them. Add the source at the end of a figure caption or in a note following a table.

Example:

Source: Hansen, W.L.; Pearton, S.J.; Haller, E.E. (1984). Appl Phys. Lett. 44:606.

Spaces

Use only one space between a period and the beginning of the next sentence.

Standard Errors

Express standard measurement errors as shown below.

Example:

6.0 nm ± 0.2 nm

States and Countries

States

In text, consistently spell out states' names rather than using U.S. Postal Service abbreviations.
Examples:
- California (rather than CA)
- Colorado (rather than CO)
- Wyoming (rather than WY)
You may use D.C. for the District of Columbia in text, in both formal and informal publications. When you include addresses or state names in full addresses (containing streets and cities), contact lists, reference lists, and bibliographies, however, you may use the following abbreviations:

AL, AK, AZ, AR, CA, CO, CT, DC, DE, FL, GA, HI, ID, IL, IN, IA, KS, KY, LA, ME, MD, MA, MI, MN, MS, MO, MT, NE, NV, NH, NJ, NM, NY, NC, ND, OH, OK, OR, PA, RI, SC, SD, TN, TX, UT, VT, VA, WA, WV, WI, WY (PR, VI).
Countries

Do not abbreviate the names of countries (including the United States) when they are used as nouns. Use U.S. as the adjective form.
Examples:
- the United States
- U.S. DOE program
- U.S. population

Table Data

See data in tables.

Taxonomic Names

See capitalization and italics.

Telephone Numbers and Addresses

See addresses and phone numbers.

Temperature

Use a degree symbol (º) with temperatures expressed in the Celsius and Fahrenheit scales but not with kelvins (just use K). Don't leave a space between the number and the letter for ºC and ºF, but leave a space between the number and K.

Examples:

72°F

0 K

That and Which

See which and that, nonrestrictive phrases and clauses, and restrictive phrases and clauses.

Time

Use lowercase a.m. and p.m. (with periods) to denote ante meridiem and post meridiem (before and after noon); use a lowercase s (no apostrophe) to show the plural of a decade expressed with numerals (the 1990s).

Unit Modifiers

See compound words, unit modifiers, and hyphens.

Units of Measurement

Use numerals with units of measurement and time in technical papers and reports, even when the number is less than 10. In some outreach publications, you may spell out numbers less than 10, especially with units of time. Except with $, °, and %, leave a space between the numeral and the unit.

2 kW	7 cm²	16.8%
3 m	8-hour days	300 Btu
5 years	$2 billion	45°

URLs

Uniform resource locators, or URLs, are essentially Web addresses. On Web sites, URLs should be embedded in text.

Example:

More information is available from EERE.

In print, URLs should not be embedded in text. If a URL extends beyond one line of text, add a break at a solidus.

Web Site

Web site and Web page are both written as two words. Web should be capitalized.

Which and That

Standard American English uses which for nonrestrictive or nondefining phrases and clauses and that for restrictive or defining phrases and clauses. The word which usually signals the approach of added, nonessential information. When a phrase or clause is not essential to the meaning of a sentence, use the relative pronoun which and enclose the phrase or clause in commas.

Example:

This paper, which she has been working on for three weeks, discusses string theory.

When a phrase or clause is essential to the meaning of a sentence (that is, the sentence would not make much sense without it), use the relative pronoun that and leave out the commas.

Example:

The paper that he completed recently will be presented in New York; the paper that he finished last summer will be presented in Philadelphia.

See Strunk and White's The Elements of Style for more on that and which.

World Wide Web

To abbreviate World Wide Web, use the Web, after writing the name out in full the first time it is mentioned.

Zero

For numbers less than one, place a zero before the decimal.

Examples:

0.5

0.125

0.00125