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.


RULE #1:

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.


RULE #2:

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).

Examples of Rule #2:
Be sure to dot your i's and cross your t's.
The instructor gave few A's in the class.

RULE #3:

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
informal writing.)

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