Apostrophes show possession, indicate a contraction (the omission of one or more letters or numbers), or are used to form the plurals of some letters and abbreviations.
Use an apostrophe to form a possessive noun or pronoun. Use the apostrophe even when the item in possession is not stated, but is implied.Examples of Rule #1:
We went to Doug's house for dinner.
We went to Doug's for dinner.
Use an apostrophe and an –s to form the plural of all lowercase letters and the capital letters A, I, M, and U.
NOTE: A, I, M, and U are the only capital letters that require an apostrophe to form the plural because, without the apostrophe, adding an –s would form a different word (A's–As, I's–Is, M's–Ms, and U's–Us).
Be sure to dot your i's and cross your t's.
The instructor gave few A's in the class.
Use an apostrophe and an –s to form the plural of a word used to refer to the word itself.Examples of Rule #3:
Make sure you cover all the if's, and's, and but's.
RULE #4:Use an apostrophe and an –s to form the plural of an abbreviation that contains periods.
Examples of Rule #4:
The university has many Ph.D.'s on its faculty.
R.N.'s who wish to further their education will like our evening program.
RULE #5:Use an apostrophe to form contractions of the words it is, do not, and who is. (Contractions are used only in
Examples of Rule #5:
It's going to be fine.
Don't play that tape.
Who's going to the movie?
RULE #6:Use an apostrophe to indicate that figures or letters have been omitted on purpose.
Examples of Rule #6:
The report was produced in '95.
Here's wishin' you luck.
RULE #7:For numbers, abbreviations without periods, and symbols used as words, the apostrophe before the –s is optional if the plural is clear.
Examples of Rule #7:
7s OR 7's
1960s OR 1960's
UFOs OR UFO's