Acronyms and other abbreviations
An abbreviation is a shortened form of a word or phrase. Depending on the abbreviation, it may be written in uppercase (ID), lowercase (tsp.), or a combination of upper- and lowercase letters (Mrs.). It may or may not include one or more periods.
An acronym is a specific type of abbreviation. Acronyms are formed from the first letter or letters of the words in a name or phrase, sometimes producing a pronounceable word (AIDS, NATO, NASA, JAMA), and sometimes not (ATM, CEO). In the United States, acronyms are usually set in all capital letters.
Sometimes an acronym will enter the language as a word with its own meaning, such as scuba, from self-contained underwater breathing apparatus.
WHEN IS AN ACRONYM AN INITIALISM?
When and how to introduce abbreviations
No matter how familiar an abbreviation may seem to you, some Web visitors—particularly those from countries other than your own—may be unfamiliar with the term. Use these guidelines for introducing acronyms and other abbreviations in your writing:
- If the shortened form of a word may be unfamiliar to your readers, spell it out the first time it’s used or include the abbreviation in parentheses following the spelled-out form.
Many sites now support RSS. RSS, which stands for Really Simple Syndication, is a method for accessing Web content. (Define in text on first use.)
Many sites now support Really Simple Syndication (RSS), a method for accessing Web content. (Spell out on first use.)
- If the shortened form is better-known than its spelled-out form (for example, ATM, USB), use the shortened form. For guidance on individual abbreviations, see the Yahoo! word list.
How to form plurals of abbreviations
To form the plural of abbreviations and acronyms, add a lowercase s. Don’t include an apostrophe unless omitting the apostrophe could cause confusion (for example, if adding an s by itself forms a word). For more examples, see “Apostrophes.”
Drs. (Plural of abbreviated title “Dr.”)
Sens. (Plural of abbreviated title “Sen.”)
PhD’s (The lowercase “h” in the middle makes this one slightly confusing without an apostrophe.)
Oakland A’s (Single-letter abbreviations, like “A” for “Athletic” here, almost always need an apostrophe and an “s” to prevent confusion—without the apostrophe, this baseball team’s name could be confused for the word “as.”)
Don’t add an s to abbreviations of units of measurement (for example, 2 in., 5 oz., 10 lb.). For more on these, see “Units of Measure.” For abbreviations of months and days when used with numbers, see “Dates.”