No apostrophes for plurals
An apostrophe typically is not used to pluralize numbers, letters, abbreviations, nouns, and words mentioned as words. Note the few exceptions and be consistent throughout your paper.
Plural of numbers
Do not use an apostrophe in the plural of any numbers.
Oksana skated nearly perfect figure 8s.
The 1920s are known as the Jazz Age.
Plural of letters
Italicize the letter and use roman (regular) font style for the -s ending. (Do not italicize academic grades.)
Two large Ps were painted on the door.
He received two Ds for the first time in his life.
exceptions: To avoid misreading, use an apostrophe to form the plural of lowercase letters and the capital letters A and I.
Beginning readers often confuse b’s and d’s.
Students with straight A’s earn high honors.
mla note: MLA recommends using an apostrophe for the plural of single capital and lowercase letters: H’s, p’s.
Plural of abbreviations
Do not use an apostrophe to pluralize an abbreviation.
Harriet has thirty DVDs on her desk.
Marco earned two PhDs before his thirtieth birthday.
Plural of nouns
Do not use an apostrophe with nouns that are not possessive.
Plural of words mentioned as words
Generally, omit the apostrophe to form the plural of words mentioned as words. If the word is italicized, the -s ending appears in roman (regular) type.
We’ve heard enough maybes.
Words mentioned as words may also appear in quotation marks. When you choose this option, use the apostrophe.
We’ve heard enough “maybe’s.”