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."
Long and short versions of a word
Some words have a long version and a short version. Examples include:
- application and app
- demonstration and demo
- synchronize and sync
The short versions of the words are not abbreviations, and if you use them, you don't need to put a period after them.
If you're not sure whether a word is an abbreviation or just a short version of a longer word, look in our preferred dictionary. If that doesn't settle the issue, use the speaking test: if you speak the short version as a word ("This is a demo version of the product"), you can usually treat it as a word and not an abbreviation.
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
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." in some circumstances.
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."
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.
- If you write or say an abbreviation as a word (for example, "app" or "sync"), don't put a period after it.
- Don't use a period with an abbreviation for the name of a US state or the District of Columbia (DC).