Apostrophes are very commonly misused. I see errors on Internet discussion boards, on signs advertising businesses, even in articles in newspapers and magazines. It is a rampant problem that is easy to correct with a little education. When you understand exactly when an apostrophe is to be used (and when it's not), you will never use one incorrectly again.Good grammar and punctuation are important to anyone who wants to write anything that anyone else is ever likely to read. They make your writing pleasant to read and easy to follow. Writing anything with bad grammar and punctuation will lose you some credibility points.Apostrophes have three basic uses: to replace missing letters or numbers, to show plurals of lowercase letters and single uppercase letters, and to indicate possession. They are not used for most plurals, which is the most common way to misuse an apostrophe.
Missing Letters or Numbers
Use an apostrophe to indicate missing letters. This occurs when you are writing a contraction, such as don’t (do not), wouldn’t (would not) or it’s (it is).
Use an apostrophe for it’s only when you are writing a contraction of it is. When writing the possessive its, do not use an apostrophe.
Use an apostrophe to indicate missing numbers. This generally occurs when you are abbreviating the year, such as “it happened back in ’99.”
Plurals of Lowercase Letters and Single Capitals
Use an apostrophe to indicate the plural of lowercase letters, such as “my typewriter won’t make n’s.”
Use an apostrophe to indicate the plural of a single uppercase letter, such as “she gets all A's in school.”
There is no other time an apostrophe should be used to make a word plural.
Do not use an apostrophe for the plural of uppercase acronyms (MREs) or numbers (the 1980s).
Use an apostrophe to indicate possession. If the noun is singular, such as girl or dog, put an apostrophe after the last letter and add an s (dog’s ball)—even if the singular noun ends in s (James’s car).
Add an apostrophe after the s if the noun is plural and ends in s, and do not add another s (girls’ ribbons).
Add an apostrophe and an s to plural nouns that do not end in s (women’s restroom).