apostrophe
The raised mark (’) that shows possession or marks letters left out of a word.
An apostrophe has two main uses. First, it shows possession. A singular noun takes ’s: the pilot’s license. A plural noun that ends in s takes the apostrophe alone: the pilots’ union. An irregular plural takes ’s: the children’s books. Second, it marks the letters left out of a contraction: don’t for do not, it’s for it is. An apostrophe also forms the plural of a lowercase letter, where the plural would otherwise be misread: mind your p’s and q’s. The possessive pronouns its, yours, hers, ours, theirs, and whose take no apostrophe. Each use of the apostrophe has its own entry, listed under Apostrophe.
Examples
UseThe teachers’ lounge is on the second floor. (The lounge belongs to many teachers, so the apostrophe follows the plural s.)
UseThey’re leaving at noon. (The apostrophe marks the letter left out of they are.)
AvoidFresh tomato’s for sale. (A plain plural takes no apostrophe; write tomatoes.)
AvoidThe company raised it’s prices. (It’s means it is; the possessive pronoun is its.)
AvoidThe band peaked in the 1990’s. (Numerals, capital letters, and abbreviations form plurals with s alone; write 1990s, three 7s, CDs.)