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).

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Google Developer Documentation Style Guide
Google Developer Documentation Style Guide