abbreviations and acronyms

An abbreviation is a shortened form of a word used in place of the full word (e.g., Inc.). An acronym is a word formed from the first letters of each of the words in a phrase or name (e.g., NREL or DOE). Abbreviations and acronyms are treated similarly in NREL publications. 

1. Using Abbreviations and Acronyms Sparingly
   Avoid using a given acronym unless you use it extensively in a publication. In a short report, do not use an acronym for a phrase you use five or fewer times. In a long report, do not use an acronym for a phrase you use fewer than 10 times. In a webpage, do not use an acronym for a phrase you use fewer than three times.

   Some two-letter abbreviations and acronyms are acceptable (e.g., AC and DC, or MW). Avoid other two-letter acronyms that are less universally used (e.g., EE and RE).

   If you use many acronyms in a report, add a list of acronyms at the beginning of the report. For an example, see this sample report.

2. Spelling out Acronyms
   In general, each time you use an acronym for the first time in the body of a report or on a given webpage, spell it out and put the acronym in parentheses after the full name. However, you do not need to spell out most common abbreviations and acronyms (e.g., AC, DC, cm, m, Hz, kW, MW, GW, and rpm) in most technical reports.

3. Abbreviating Measurement Units
   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."

   Abbreviate units of measurement when they are used with a numeral or numeric value (e.g., 900 W/m², 43 cm, or 60 Hz). With a few exceptions (such as %, °, $, and ¢), use a space to separate them from numerals.

4. Abbreviating Plurals
   Use a small s (no apostrophe) for plurals of most abbreviations. For plurals of units of measurement, omit the s (e.g., 15 cm, 6 m, 5 million Btu, 75 dB, 40 W).

5. Abbreviating Equations and References
   You can abbreviate "equation" and "reference" when you use them with numbers, but spell them out at the beginning of a sentence.

   See Eq. 1-1, Eq. 2-7, and Ref. 10.
   Equation 2-1 shows the relation.
6. Abbreviating in Journals
   For 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 Woodward Library website.