When to Use Apostrophes

Apostrophes are most often used to show possession and to show omission in contractions. They are also used to show pluralization of lowercase letters. It is oftentimes not when to use apostrophes, but when not to use apostrophes that causes confusion for people.

One of my favorite resources for grammar and punctuation is the The Blue Book of Grammar and Punctuation. They also have a wonderful section on apostrophes that goes into detail on the multiple proper uses of apostrophes, laying out the guidelines in a easy-to-read format. They also outline what I have found to be the most common mistakes people make when writing or transcribing.

1. Adding an apostrophe followed by an S shows possession and not pluralization. It's always "yours" and not "your's," and I have two daughters, not two daughter's.
   
   
2. It's always means "it is" or "it has" and never shows possession. Its is used to show possession, as in, "My city has its own summer carnival every year."
   
   
3. When used as nouns, plural forms of capital letters and numbers do not use an apostrophe.
   
   -My parents grew up in the 1960s, while I am a product of the '80s.
   
   -We'll start with the back of the alphabet and have the Xs, Ys and Zs line up first for recess.
   
   The exception to this rule would be when the apostrophe is needed for clarification, as in the case of I's, rather than Is.