Some of the most common punctuation mistakes involve the apostrophe, but you only need to learn a few basic rules to determine whether you are using this punctuation mark correctly. The apostrophe denotes possession, some plural forms and is used in contractions.

Singular Possessive

Place an apostrophe between the end of a name followed by whatever they are in possession of. Example: You will need to ride in Mary's car.

Names Ending in "S"

If the name of the one who owns something ends in "s," it is acceptable to leave out the second "s" after the apostrophe. Example: This is Jess' car.

Objects Cannot Possess

Objects cannot possess anything, so if you are referring to part of an object, leave out the apostrophe. Example: The bike fell on its side.

Plural Ending in "S"

When showing possession of plural subjects in which the word ends with an "s," place the apostrophe after the word and do not add another "s." Example: These are the actresses' dresses.

Plural Specific Possessive

When showing possession by more than one person, place the apostrophe and "s" after the last name in the sentence. Example: This is Bob and Jane's house.

Contractions

Place an apostrophe in the middle of word to show a contraction, which is a combination of two words that's shortened for convenience. For example: Rita said she'll work over tonight. "She'll" is a contraction of "she" and "will" in the sentence. Another example: It's getting close to show time. "It's" is a contraction of "it" and "is" in the sentence.

Plural Lowercase Letters

While showing a plural form of something with which the meaning would be unclear with just an "s," add an apostrophe. Example: Please remember to dot your I's and cross your T's.

Shortened Forms

When shortening a decade by taking away the first part of the number, place an apostrophe in front of the shortened form. Example: Joe likes learning about the '20s. The "'20s" is referring to the "1920s" in the sentence. Use this form as long as it is clear that you are talking about the 1920s and not the 1820s or 1720s.

Plural Names

Do not use an apostrophe to show the plural form of a name. For example, I met the Smiths today.

Capital Letters Ending in "S"

Do not place an apostrophe after capital letters as a shortened form, or after a decade. For instance, Jeff learned his ABCs in the 1990s.