Apostrophe Rules: How to Use Apostrophes Correctly

The apostrophe does two jobs in English: it shows possession (Sam's book) and it marks missing letters in contractions (don't, it's). It is also one of the most misused marks in the language. This guide covers every apostrophe rule, the tricky cases that trip up even careful writers, the mistakes to avoid, and a short quiz to test yourself.

Quick Answer: What Does an Apostrophe Do?

Possession.
Add 's to show something belongs to someone: Sam's book, the cat's toy, the children's playground.

Contractions.
Mark where letters are missing when two words combine: do not becomes don't, it is becomes it's.

Never for plurals.
Apostrophes do not make words plural. Lemons, not lemon's. The 1990s, not the 1990's.

Never on possessive pronouns.
Yours, his, hers, ours, theirs, and its never take an apostrophe.

The James's vs James' question.
Both are correct. Chicago style recommends James's; AP style prefers James'. Pick one and stay consistent.

What Is an Apostrophe?

An apostrophe is a punctuation mark with two main functions in English writing. It shows that something belongs to someone or something, which is called possession, and it marks where letters have been omitted when two words are combined into one, which is called a contraction. Understanding those two functions resolves almost every everyday apostrophe question. A third, much rarer use covers the plural of single letters, which is explained near the end of this guide.

Apostrophe Rules at a Glance

Use an apostrophe for	Do not use one for	Example
Singular possession	Simple plurals	Sam's book (not lemon's for sale)
Plural possession	Possessive pronouns	the cats' toys (not it's tail)
Contractions	Decades and acronyms	don't, it's (not the 1990's, DVD's)
Plural of single letters	Verb endings	mind your p's and q's

How to Use Apostrophes for Possession

To show that something belongs to a person or thing, add an apostrophe and an "s" after the noun.

Sam's book means the book belongs to Sam. Sam's book is on the table.
The cat's toy means the toy belongs to the cat. The dog is playing with the cat's toy.
The children's playground means the playground belongs to the children. I heard laughter from the children's playground.

Singular Possessive

For singular nouns, add 's to show possession. This rule applies even when the singular noun already ends in "s," though some style guides allow exceptions for proper nouns.

The cat's toy (one cat). The cat's toy is in the corner by the dog's bone.
James's car (belongs to James). I left my coat in James's car.
The boss's office (one boss). The meeting is in the boss's office at 10 a.m.

Plural Possessive

For plural nouns that already end in "s," add only an apostrophe after the "s." For irregular plurals that do not end in "s" (children, women, people), add 's.

The cats' toys (multiple cats). The cats' toys are scattered across the living room.
The Smiths' house (the family named Smith). We went over to the Smiths' house yesterday.
The women's department (irregular plural). The women's department is on the second floor.

The James's vs. James' rule. For singular proper nouns ending in "s" (James, Charles, Davis), Chicago Manual of Style recommends adding 's (James's, Charles's). AP Stylebook recommends only an apostrophe (James', Charles'). Both are acceptable. Be consistent within a single document.

How to Use Apostrophes for Contractions

An apostrophe replaces the missing letter or letters when two words are combined into a contraction. Contractions are widely accepted in most modern writing, including academic and business contexts, though some traditional style guides still discourage them in formal documents.

Don't (do not). The reviewers don't usually request major revisions.
She's (she is or she has). She's the lead author on three published papers.
They're (they are). They're presenting their findings at the conference next week.
It's (it is or it has). It's been two weeks since the manuscript was submitted.

Tricky Apostrophe Cases

A handful of cases come up often enough in professional writing to need their own attention. Each one trips up writers who otherwise apply the basic rules well.

Joint vs. Separate Possession

When two people own something together, add 's to the second name only. When two people own separate things, add 's to each name.

Joint: Cesar and Maribel's home is constructed of redwood. (One home, owned by both.)
Separate: Cesar's and Maribel's homes are both lovely. (Two homes, one belonging to each.)

Compound Nouns

For singular compound nouns, add 's at the end of the full term. For plural compound nouns, form the plural first, then add 's.

My mother-in-law's recipe is the best in the family.
The attorney-general's statement was released yesterday.
My two brothers-in-law's birthdays fall in the same week.

Family Names

Family names cause some of the most common errors. The rule depends on whether you are pluralizing or showing possession.

The Smiths means the family. The Smiths are coming for dinner.
The Smiths' house means the house belonging to the Smith family. We went to the Smiths' house.
The Smith's house would mean the house belonging to one person named Smith. Use only when referring to one Smith, not the whole family.
For names ending in "s," "x," "z," "ch," or "sh," add "es" to form the plural: the Joneses, the Martinezes, the Foxes, the Sanchezes.

"For Goodness' Sake" and Similar Phrases

Some traditional phrases drop the second "s" in the possessive to avoid awkward sound repetition. The apostrophe stays.

For goodness' sake (not "goodness's sake")
For conscience' sake (not "conscience's sake")
For old times' sake (a plural possessive that follows the same sound-based logic)

Common Apostrophe Mistakes

1. The Greengrocer's Apostrophe

This mistake is named for the apostrophes that often appear on produce signs. It involves adding an apostrophe to a basic plural, which is never correct. Plurals do not take apostrophes.

Incorrect: Fresh lemon's for sale. Correct: Fresh lemons for sale.
Incorrect: The Johnson's are coming for dinner. Correct: The Johnsons are coming for dinner.

2. Its vs. It's

Confusing "its" and "it's" is the single most common apostrophe error in English writing. The rule is simple. "It's" always means "it is" or "it has." If you cannot substitute either of those phrases into the sentence, use "its" without an apostrophe. "Its" is the possessive form of "it," like his or hers, neither of which takes an apostrophe.

Incorrect: The dog lifted it's leg. Correct: The dog lifted its leg. (possessive)
Incorrect: Its going to rain tomorrow. Correct: It's going to rain tomorrow. (it is)

For a complete explanation with more examples, see our guide on its vs. it's.

3. Decades and Acronyms

Do not use an apostrophe when pluralizing decades or acronyms. The apostrophe would imply possession, which is not the meaning intended.

Incorrect: music from the 1990's. Correct: music from the 1990s.
Incorrect: several DVD's. Correct: several DVDs.
Incorrect: three new CEO's. Correct: three new CEOs.

The exception is for plurals of single lowercase letters, where an apostrophe prevents misreading: mind your p's and q's.

4. Possessive Pronouns Never Take Apostrophes

The possessive pronouns yours, his, hers, ours, theirs, and its never take apostrophes. This trips up many writers because most other possessives do use apostrophes.

Incorrect: The book is your's. Correct: The book is yours.
Incorrect: That decision is their's to make. Correct: That decision is theirs to make.

Memory Tricks That Always Work

The missing-letters trick. An apostrophe in a contraction always marks where letters were removed. If letters can be added back ("it is" or "do not"), use the apostrophe. If nothing was removed, no apostrophe is needed.
The possessive pronoun trick. Possessive pronouns never take apostrophes. If you would not write her's or your's, do not write it's when you mean possession.
The plural test. Apostrophes show possession or contraction, never a simple plural. Lemons, not lemon's. The Johnsons, not the Johnson's.

Quiz: Test Your Apostrophe Knowledge

Choose the correctly punctuated option in each question below.

Family possession: Which shows the house belonging to the whole Smith family?
- a) The Smiths' house
- b) The Smiths's house
- c) The Smith's house
Its or it's:
- a) Its time to begin.
- b) It's time to begin.
- c) Its' time to begin.
Pluralizing a decade:
- a) Music from the 1980's was distinctive.
- b) Music from the 1980s was distinctive.
- c) Music from the 1980s' was distinctive.
Joint possession:
- a) Cesar's and Maribel's home is on the corner.
- b) Cesar and Maribel's home is on the corner.
- c) Cesars and Maribels home is on the corner.
Possessive pronoun:
- a) The decision is theirs to make.
- b) The decision is their's to make.
- c) The decision is theirs' to make.

Answers: 1-a (plural possessive of the family name); 2-b (it is time); 3-b; 4-b (joint possession); 5-a (possessive pronouns take no apostrophe).

Frequently Asked Questions

What is an apostrophe used for?

An apostrophe has two main uses in English. First, it shows possession, meaning that something belongs to someone or something, as in Sam's book or the cat's toy. Second, it marks where letters have been omitted in a contraction, as in do not becoming don't or it is becoming it's. A rare third use forms the plural of single letters, as in mind your p's and q's. An apostrophe is never used to make an ordinary word plural.

When do you use an apostrophe to show possession?

To show possession, add an apostrophe and an s to a singular noun, as in Sam's book or the boss's office. For a plural noun that already ends in s, add only an apostrophe after the s, as in the cats' toys or the Smiths' house. For an irregular plural that does not end in s, such as children or women, add apostrophe s: the children's playground, the women's department.

Is it James's car or James' car?

Both forms are correct depending on which style guide you follow. Chicago Manual of Style recommends adding apostrophe s to all singular nouns ending in s, including proper nouns: James's car. AP Stylebook recommends adding only an apostrophe to singular proper nouns ending in s: James' car. Most academic, book, and corporate publishing follows Chicago. Most journalism follows AP. Choose one style and apply it consistently throughout your document.

What is the difference between its and it's?

It's is a contraction of it is or it has, and always takes an apostrophe. Its is the possessive form of it, and never takes an apostrophe. The simplest test: if you can replace the word with it is or it has and the sentence still makes sense, use it's. Otherwise use its. For example, it's raining works as it is raining, so use it's. The dog wagged its tail does not work as the dog wagged it is tail, so use its.

Do you use an apostrophe to make a word plural?

No. Apostrophes show possession or mark contractions, never simple plurals. Write lemons, not lemon's, and the Johnsons, not the Johnson's, when referring to the family. The same applies to decades and acronyms: write the 1990s and DVDs, not the 1990's and DVD's. The one narrow exception is the plural of a single lowercase letter, where an apostrophe prevents misreading, as in mind your p's and q's.

Do possessive pronouns take apostrophes?

No. The possessive pronouns yours, his, hers, ours, theirs, and its never take an apostrophe. This trips up many writers because most other possessives do use one. Write the book is yours, not your's, and the decision is theirs, not their's. Remembering that its belongs to this group is the key to never confusing it with it's.

What are the most common apostrophe mistakes?

The most common apostrophe errors are using apostrophes in basic plurals (oranges, not orange's), confusing its with it's, misplacing the apostrophe in plural possessives (the Smiths' house, not the Smith's house when referring to the whole family), adding apostrophes to acronyms and decades (DVDs not DVD's, 1980s not 1980's), and adding apostrophes to possessive pronouns (yours, not your's). Each of these is corrected by remembering that apostrophes show possession or omission, never plurality.

How do I show joint possession with two names?

When two people own something together, add apostrophe s to the second name only. Cesar and Maribel's home means they share one home. When two people own separate things, add apostrophe s to each name. Cesar's and Maribel's homes means each person has their own home. The placement of the apostrophe signals whether the ownership is joint or separate.

Where does the apostrophe go, before or after the s?

The apostrophe goes before the s for a singular possessive (the cat's toy, one cat) and after the s for a plural possessive when the plural already ends in s (the cats' toys, several cats). So the position of the apostrophe tells the reader whether one owner or many owners is meant. For irregular plurals that do not end in s, such as children, the apostrophe comes before the s: the children's books.

Related Punctuation and Word-Choice Guides

Apostrophes are one of several punctuation and word-choice areas that consistently trip up writers. For more, see our guides on its vs. it's, hyphen rules and when to use them, and which vs. that.

When to Get Help with Your Writing

Misplaced apostrophes are small errors, but reviewers, instructors, and clients notice them, and AI grammar checkers regularly miss them. Automated tools flag obvious misspellings but often pass over placement issues like "the Smith's house" when the whole family is meant, and some autocorrect tools introduce errors by changing its to it's automatically. A human editor catches what automated tools do not.

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