Apostrophe Rules: Possessives, Contractions, and Common Errors

The apostrophe is a small mark that causes big problems. It has just two main jobs in English — showing possession and forming contractions — yet apostrophe rules trip up writers of all levels. Apostrophe errors are among the most common mistakes in written English, appearing everywhere from student essays to professional signs and advertisements.

This comprehensive guide covers every apostrophe rule you need, including the tricky special cases that cause the most confusion. By the end, you will have a clear, reliable system for using apostrophes correctly in any situation.

What Is an Apostrophe?

An apostrophe (') is a punctuation mark used primarily in two ways: to indicate that something belongs to someone or something (possession), and to show that letters have been omitted from a word (contractions). It is not used to form plurals, despite what countless shop signs would have you believe.

Apostrophes for Possession

Singular Possession

To show that a singular noun possesses something, add an apostrophe followed by the letter "s" ('s):

• "the dog's bone" (the bone belonging to the dog)
• "Sarah's book" (the book belonging to Sarah)
• "the company's policy" (the policy of the company)
• "the child's toy" (the toy belonging to the child)

This rule applies even when the singular noun already ends in "s":

• "James's car" (the car belonging to James)
• "the boss's office" (the office of the boss)
• "Charles's decision" (the decision made by Charles)

Some style guides (notably the Associated Press) prefer dropping the extra "s" after a singular noun ending in "s": "James' car" instead of "James's car." Both forms are acceptable — just be consistent within a single piece of writing. The Chicago Manual of Style and most academic guides recommend the full "'s" form.

Plural Possession

For plural nouns that end in "s," add only an apostrophe after the existing "s":

• "the dogs' bones" (bones belonging to multiple dogs)
• "the students' assignments" (assignments belonging to multiple students)
• "the teachers' lounge" (the lounge for teachers)
• "my parents' house" (the house of my parents)

For plural nouns that do not end in "s" (irregular plurals), add "'s" just as you would for a singular noun:

• "the children's playground" (the playground for children)
• "the women's department" (the department for women)
• "the people's choice" (the choice of the people)
• "the men's restroom" (the restroom for men)

Joint vs. Individual Possession

When two or more people own the same thing jointly, add "'s" only to the last name:

• "Jack and Jill's house" (They share one house.)

When two or more people own separate things, add "'s" to each name:

• "Jack's and Jill's cars" (They each have their own car.)

Compound Nouns

For compound nouns, add "'s" to the end of the compound:

• "my mother-in-law's recipe"
• "the attorney general's opinion"
• "someone else's problem"

Apostrophes in Contractions

A contraction is a shortened form of a word or pair of words, with an apostrophe marking the spot where letters have been removed. Contractions are standard in informal and conversational writing, though many style guides recommend avoiding them in formal writing.

Common Contractions

Its vs. It's

This is the single most common apostrophe error in English, so it deserves special attention. The confusion arises because the rules for possessives and contractions seem to contradict each other.

• It's = "it is" or "it has" (contraction). The apostrophe replaces the missing letter(s).
• Its = belonging to it (possessive). No apostrophe.

Examples:

• "It's raining outside." (It is raining.)
• "It's been a long day." (It has been.)
• "The dog wagged its tail." (The tail belonging to it.)
• "The company raised its prices." (The prices belonging to the company.)

The test: Try substituting "it is" or "it has." If the sentence makes sense, use "it's." If not, use "its."

The reason "its" has no apostrophe is that possessive pronouns never take apostrophes. Just as you would never write "hi's," "her's," or "their's," you should never write "it's" as a possessive. For more on this topic, see our guide on its vs. it's.

Apostrophes and Plurals

This is the golden rule that is most often broken: apostrophes do not form plurals. The so-called "greengrocer's apostrophe" — placing an apostrophe before the "s" in a plural noun — is always wrong.

• Wrong: "Fresh apple's for sale" → Right: "Fresh apples for sale"
• Wrong: "The Smith's live next door" → Right: "The Smiths live next door"
• Wrong: "I have three cat's" → Right: "I have three cats"
• Wrong: "Sale on TV's" → Right: "Sale on TVs"

The Rare Exception

Some style guides permit an apostrophe to form the plural of lowercase letters to prevent misreading:

• "Mind your p's and q's." (Without the apostrophe, "ps" could be confusing.)
• "She received all A's on her report card."

However, numbers and uppercase letters generally do not need an apostrophe: "the 1990s" (not "1990's"), "two PhDs" (not "PhD's").

Special Cases

Time Expressions

Apostrophes are used in expressions of time when time "possesses" something:

• "a day's work" (the work of a day)
• "two weeks' notice" (notice of two weeks)
• "a year's experience" (experience of a year)
• "three hours' delay" (a delay of three hours)

For Clarity's Sake

Some idiomatic expressions use apostrophes: "for goodness' sake," "for appearance's sake," "for conscience' sake."

Whose vs. Who's

Like its/it's, this pair causes confusion:

• Who's = "who is" or "who has" (contraction)
• Whose = belonging to whom (possessive)

You're vs. Your

Another frequently confused pair covered in our guide on your vs. you're:

• You're = "you are" (contraction)
• Your = belonging to you (possessive)

They're vs. Their vs. There

A three-way confusion covered in our guide on there, their, and they're:

• They're = "they are" (contraction)
• Their = belonging to them (possessive)
• There = in that place (adverb)

Common Apostrophe Errors

1. Greengrocer's apostrophe: Using apostrophes to form plurals ("tomato's" instead of "tomatoes"). Never do this.
2. Its/it's confusion: Using "it's" as a possessive or "its" as a contraction. Remember: "it's" always means "it is" or "it has."
3. Misplacing the apostrophe in plurals: Writing "the boy's room" when you mean "the boys' room" (multiple boys). Check whether the possessor is singular or plural before placing the apostrophe.
4. Forgetting the apostrophe in contractions: Writing "dont" or "isnt" instead of "don't" or "isn't."
5. Adding apostrophes to decades: "The 1960's" is incorrect for the plural. Write "the 1960s." Use the apostrophe only if letters are omitted: "the '60s."
6. Apostrophes with possessive pronouns: Writing "her's," "their's," or "our's." Possessive pronouns never take apostrophes: hers, theirs, ours, yours, its.

Quick Reference Table

The apostrophe may be the most misused punctuation mark in English, but its rules are actually straightforward. It shows possession and marks contractions — nothing more. If you remember that apostrophes never form plurals and that possessive pronouns never take apostrophes, you will avoid the vast majority of errors. When in doubt, ask yourself: am I showing possession, or am I shortening two words into one? If the answer is neither, you probably do not need an apostrophe.