Acronyms and Abbreviated Terms

A true acronym is formed by using the first letter from two or more separate words, for example, DEC for Digital Equipment Corporation. Articles or prepositions falling in between (for example, and, of, in, the) are generally not used as part of the acronym. Use all capitals only for true acronyms.

Many acronyms/abbreviated terms used for measurements are traditionally all lowercase, for example, cpi (characters per inch) and dpi (dots per inch). A few are mixed, such as kHz (kilohertz). Capitalization also can differ depending on meaning, for example, MW (megawatt) and mW (milliwatt). See the alphabetical section when in doubt.

As a general rule, spell out all acronyms on first use, but don't use initial capitals just because the letters form the acronym. There must be another reason for the caps; for example, the words constitute a proper noun. In other words, CAD is computer-aided design, not Computer-Aided Design.

Exceptions to the spell-out-on-first-use rule are acronyms so well known to a particular magazine or publication's readers that spelling them out would be insulting. In the alphabetical section, the Style Guide Committee has determined that acronyms marked with an asterisk are so familiar to all our readers that they don't need to be spelled out on first use. Examples include RAM, ROM, and CD-ROM.

Put the acronym in parentheses immediately after the spelled-out term. In long articles with unfamiliar acronyms, it helps to spell out the words occasionally throughout to refresh readers' memories and aid those who browse. If an article includes many unfamiliar acronyms, consider creating a glossary or sidebar.

Use judgment before allowing a short common term to be reduced to an acronym (for example, operating system to OS). Readers have difficulty with articles that read like alphabet soup.

Provided that an acronym isn't visually distracting (use your judgment), capitalize it as the author submitted it, so long as the CS Style Guide doesn't already prescribe a style for it and its formatting agrees with the official version. (For example, the www.flossproject.org provides the project's preferred capitalization: FLOSS.) When deciding whether to revise acronym capitalization, first consider clarity, followed by author preference.

The alphabetical section of the Style Guide includes combinations of words and acronyms, such as MiniDIP, which generally follow both capitalization and acronym rules.

For units of measurement, you don't need to spell out common abbreviations (such as s, min., and ms). For unfamiliar units of measurement, spell them out on first use.