Abbreviations include acronyms, initialisms, shortened words, and contractions.
- An acronym is formed from the first letters of words in a phrase, but is
pronounced as if it were a word itself:
- NATO for North Atlantic Treaty Organization.
- scuba for self-contained underwater breathing apparatus.
- An initialism is also formed from the first letters of words in a phrase,
but each letter is pronounced separately:
- CIA for Central Intelligence Agency.
- FYI for For Your Information.
- PR for Public Relations.
- A shortened word is just part of a word or phrase, sometimes with a
period at the end:
- Dr. for doctor.
- etc. for et cetera.
- min for minutes.
- CA for California.
- Contractions are discussed in a separate page of this style guide.
There's some overlap among those categories. In particular, some abbreviations can be either acronyms or initialisms, depending on the speaker's preference; examples include FAQ and SQL. In some cases, the pronunciation determines whether to use "a" or "an."
When to spell out a term
In general, when an abbreviation is likely to be unfamiliar to the audience, spell out the first mention of the term in the text (not in a heading) and immediately follow with the abbreviation, in parentheses. For all subsequent mentions of the abbreviation, use the abbreviation by itself.
Abbreviations not to use
Use the most common form of a word. If the full spelled-out word is common and easily understandable, use that rather than abbreviating. For example, write "approximately" instead of "approx."
Prefer English terms over Latin abbreviations. Don't use "i.e." or "e.g."; instead, use "that is" or "for example," respectively. One exception: it's okay to use "etc."
Periods with abbreviations
Follow these guidelines:
- Don't use periods with acronyms or initialisms.
- Put a period at the end of a shortened word, except for date and time abbreviations.
- Don't use a period with an abbreviation for the name of a US state or the District of Columbia (DC).