Apostrophes show possession (ownership), 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.
- When the noun or pronoun is singular, put the apostrophe after the last letter in the noun and then add an s.
- The dog’s collar is red.
- Smith’s theory validates these findings
- When the noun or pronoun is plural, just add an apostrophe to the end of the word.
- The dogs’ collars are red.
- The participants’ responses were anonymous.
- Use the apostrophe even when the item in possession is not stated, but is implied.
- We went to Doug's house for dinner.
- We went to Doug's for dinner.
- Lowercase letters and the capital letters A, I, M, and U
Use an apostrophe and an –s to form the plural of all lowercase letters and the capital letters A, I, M, and U.
- Be sure to dot your i's and cross your t's.
- The instructor gave few A's in the class.
- Words used to refer to themselves
Use an apostrophe and an –s to form the plural of a word used to refer to the word itself.
- Make sure you cover all the if's, and's, and but's.
- Abbreviation that contains periods
Use an apostrophe and an –s to form the plural of an abbreviation that contains periods.
- The university has many Ph.D.'s on its faculty.
- R.N.'s who wish to further their education will like our evening program.
- Forming contractions
Use an apostrophe to form contractions of the words it is, do not, and who is. (Contractions are used only in informal writing.)
- It's going to be fine.
- Don't play that tape.
- Who's going to the movie
- Omitting letters
Use an apostrophe to indicate that figures or letters have been omitted on purpose.
- The report was produced in '95.
- Here's wishin' you luck.
- Abbreviation without periods and symbols
For numbers, abbreviations without periods, and symbols used as words, the apostrophe before the –s is optional if the plural is clear.
- 7s OR 7's
- 1960s OR 1960's
- UFOs OR UFO's