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.
- It generally isn't necessary to put the acronym in parentheses immediately after the spelled-out term if the acronym is used in the sentence immediately following the spelled-out occurrence. However, if the connection isn't apparent, provide the acronym parenthetically. 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.
- In general, use only an initial capital for acronyms of five or more letters that form a pronounceable word, for example, Eprom (erasable programmable read-only memory). This makes the text easier to read. There are exceptions, however (see the alphabetical section), and clarity should always take precedence. This format should not be applied to pronounceable acronyms of five or more letters that represent the name of an organization, for example, JEDEC (Joint Electron Device Engineering Council).
- Company, product, and language names follow the same rules applied to other acronyms. A company's or public relations firm's wishes about the use of acronyms carry little weight. Explaining that the CS has a carefully thought-out rationale that is applied fairly across the board usually mitigates objections.
A few exceptions to the acronym rules are permitted, usually where widespread usage has preempted our efforts. Intel's parallel processor, which keeps the name iPSC, is one example, and there are other “grandfathered” exceptions.
The alphabetical section of the Style Guide includes combinations of words and acronyms, such as MiniDIP, which generally follow both capitalization and acronym rules.