Apostrophe Rules: When and How to Use Apostrophes

The Two Jobs of an Apostrophe

The apostrophe (') is a small mark with a focused purpose. In English, it does exactly two things: it shows that something belongs to someone or something (possessives), and it shows that letters have been omitted from a word or phrase (contractions). That's the whole job description.

Most apostrophe errors happen because writers add them where they are not needed (chiefly, in plain plurals) or leave them out where they are required. This guide walks through every situation you will encounter, with clear examples for each case.

For a broader look at how punctuation marks work together, see our guide on how to use commas. You can also run your writing through our punctuation checker to catch apostrophe errors automatically.

Possessive Apostrophes: The Basics

A possessive apostrophe signals that a noun owns or is associated with something. The general pattern is straightforward: add an apostrophe and the letter s to a singular noun, and add just an apostrophe to a plural noun that already ends in s. Exceptions exist, and they are covered below.

Singular Nouns

For most singular nouns, the rule is simple: add 's.

• the cat's bowl (the bowl belonging to the cat)
• the student's essay (the essay belonging to the student)
• the company's policy (the policy of the company)
• a week's notice (a notice equivalent to a week)

This applies even when the noun is an organization, an idea, or an inanimate object, not just a living creature.

Singular Nouns Ending in S

This is the rule that generates the most debate. When a singular noun already ends in s (like James, class, or boss), style guides disagree about whether to add 's or just an apostrophe.

The Chicago Manual of Style recommends always adding 's to singular nouns, regardless of their ending:

• James's car
• the boss's office
• Charles's speech

AP Style, used by most journalists, allows just an apostrophe after the final s:

• James' car
• the boss' office

Both forms are grammatically acceptable in standard English. Pick one and apply it consistently within a single document. In academic writing, James's is the more widely accepted choice. In journalism, James' is the norm.

One clear exception: classical and biblical names traditionally use only the apostrophe, with no added s. Jesus' teachings, Moses' laws, and Socrates' philosophy are the conventional forms.

Plural Nouns Ending in S

For plural nouns that already end in s, add only an apostrophe after the final s.

• the cats' water bowls (the water bowls belonging to multiple cats)
• the students' essays (the essays belonging to multiple students)
• the companies' policies (the policies of multiple companies)
• my parents' house (the house belonging to my parents)

A useful way to double-check: write out the noun first, then decide where the apostrophe goes. If the plural is cats, the possessive is cats'. If the plural is student (singular), the possessive is student's.

Irregular Plural Nouns

Some nouns form their plurals by changing spelling rather than adding s: words like children, women, men, mice, and feet. Because these plurals do not end in s, they follow the singular rule: add 's.

• the children's toys
• the women's team
• the mice's nest

Possessives with Compound Nouns

When the possessor is a compound noun (a noun made up of more than one word), the apostrophe and s go on the last word only.

• my mother-in-law's recipe
• the attorney general's decision
• the editor in chief's column

This also applies to compound nouns that name organizations or institutions:

• the Secretary of State's announcement
• the Board of Directors' report

Joint Possession vs. Separate Possession

When two people own or share the same thing, only the second name takes 's. When each person owns their own version of something, both names take 's.

The logic is consistent: the apostrophe attaches to the noun that immediately precedes the thing being possessed. If ownership is shared, only the final owner's name needs the apostrophe.

Pronouns and Apostrophes

This is the section that trips up more writers than any other. The rule is absolute: possessive pronouns never take apostrophes. They are already possessive on their own and need no extra punctuation.

The possessive pronouns are: my, mine, your, yours, his, her, hers, its, our, ours, their, theirs, whose. None of them ever get an apostrophe. For a full breakdown of how pronouns work, see our guide on what is a pronoun.

Its vs. It's

Its (no apostrophe) is the possessive form of it. It's (with apostrophe) is always a contraction meaning it is or it has. The two forms are not interchangeable.

Wrong: The dog wagged it's tail.
Right: The dog wagged its tail.

Test: substitute "it is." "The dog wagged it is tail" makes no sense, so no apostrophe belongs here.

Wrong: Its going to rain this afternoon.
Right: It's going to rain this afternoon.

Test: substitute "it is." "It is going to rain" makes perfect sense, so the apostrophe is correct.

Whose vs. Who's

Whose (no apostrophe) is the possessive form of who. Who's (with apostrophe) is a contraction of who is or who has.

Wrong: Who's jacket is this?
Right: Whose jacket is this?

Test: substitute "who is." "Who is jacket is this?" makes no sense, so no apostrophe belongs.

Wrong: I wonder whose coming to the party.
Right: I wonder who's coming to the party.

Test: substitute "who is." "I wonder who is coming to the party" works fine, so the apostrophe is correct.

The same substitution test works for every pronoun/contraction pair. If you can replace the word with its expanded form and the sentence still makes sense, use the apostrophe. If it breaks the sentence, leave the apostrophe out.

Contractions

Contractions are shortened forms of words or phrases where an apostrophe marks the spot where letters were removed. They are perfectly correct in most writing contexts, though formal academic or legal writing typically avoids them.

Notice that the apostrophe always sits exactly where the missing letter or letters would be, not at the junction of the two words. Don't has the apostrophe between n and t because the o from not was removed. We're has it between e and r because the a from are was removed.

One irregular contraction worth noting: won't is the contracted form of will not, even though the spelling looks nothing like will not. This is a historical quirk of English with no clean logic to untangle. You simply have to know it.

Common Apostrophe Mistakes

Apostrophes in Plurals (The Greengrocer's Apostrophe)

The single most common apostrophe error is adding one to a plain plural. Apostrophes have no role in forming standard plurals. The mistake is common enough that it has an informal name: the "greengrocer's apostrophe," from the hand-lettered signs that once advertised "apple's, pear's, and plum's" at market stalls.

Wrong: The 1990's were a decade of rapid change.
Right: The 1990s were a decade of rapid change.

Wrong: We offer three different package's for new customer's.
Right: We offer three different packages for new customers.

Wrong: The Smith's moved to Denver last year.
Right: The Smiths moved to Denver last year.

(Unless you mean something belonging to the Smiths, in which case "the Smiths' house" is correct.)

The rule holds for all regular plurals: decades (the 1980s, not the 1980's), surnames used as family names (the Joneses, not the Jones's), and common nouns like menus, pizzas, and laptops. None of these need apostrophes to become plural.

Confusing Their, There, and They're

Their is the possessive pronoun (no apostrophe). They're is the contraction of they are. There refers to a place or introduces a sentence.

Wrong: They're going to there house after the game.
Right: They're going to their house after the game.

Confusing Your and You're

Your is the possessive pronoun. You're is the contraction of you are.

Wrong: Your going to love this restaurant.
Right: You're going to love this restaurant.

Wrong: I love you're new haircut.
Right: I love your new haircut.

Apostrophes with Abbreviations and Numbers

Abbreviations and numbers follow the same logic as other nouns. To form the plural of an abbreviation, simply add s with no apostrophe:

• She has two MBAs on her team. (not MBA's)
• He scored in the 90s on every test. (not 90's)
• The CVs were reviewed by the panel. (not CV's)

There is one narrow exception: when adding just an s would make a lowercase abbreviation unreadable, an apostrophe is acceptable for clarity. Writing mind your p's and q's uses apostrophes because ps and qs look ambiguous. For capital letters and most abbreviations, however, no apostrophe is needed: the 1980s, three CEOs, two PhDs.

To show possession with an abbreviation, the standard rule applies: the CEO's statement, the EPA's report.

Quick-Reference Apostrophe Cheat Sheet

Apostrophes in Names Ending in S

Names that end in s cause genuine confusion because the two dominant style guides disagree, and writers encounter both conventions in published work. Here is a practical summary:

• In books, academic papers, and most formal writing, follow Chicago: Keats's poems, Thomas's idea, Texas's economy.
• In news articles and press releases, follow AP: Keats' poems, Thomas' idea, Texas' economy.
• For names from classical antiquity or scripture (Achilles, Sophocles, Jesus, Moses), use the apostrophe alone in nearly all style guides: Achilles' heel.
• When a name ends in a silent s sound (such as the French name Camus), Chicago still recommends Camus's, though some writers prefer Camus'.

Whichever convention you choose, apply it consistently throughout your document. Mixing James's in one paragraph with Charles' in the next looks careless and inconsistent.

Frequently Asked Questions About Apostrophes

Should I write "it's" or "its" when describing what something has?

If you mean possession (something belonging to it), use its without an apostrophe: "The company released its annual report." The possessive pronoun needs no apostrophe. Use it's only when you mean it is or it has: "It's been three years since the last audit." When in doubt, expand the word. If "it is" or "it has" fits in its place, write it's. If it does not fit, write its.

Do decades need apostrophes: "the 1980s" or "the 1980's"?

No apostrophe. The correct form is the 1980s. The decade is a plain plural, not a possessive. "The 1980's" implies that something belongs to 1980, which is rarely what anyone means. The same rule applies to decades written out as words: the eighties, not the eightie's. If you are showing possession by a decade (uncommon but grammatically possible), then an apostrophe is correct: "the 1980s' most influential films."

How do I make a family name plural, like "the Smiths" or "the Joneses"?

To refer to an entire family, simply pluralize the surname with no apostrophe: the Smiths, the Joneses, the Garcias, the Murphys. Names ending in s, x, z, ch, or sh take -es: the Joneses, the Marxes. No apostrophe is involved in any of these. Reserve the apostrophe for when you want to show possession: the Smiths' driveway, the Joneses' holiday card.

Is "who's" ever a possessive?

No. Who's is only ever a contraction of who is or who has. The possessive form of who is whose, with no apostrophe. "Whose coat is this?" asks who owns the coat. "Who's coming to dinner?" asks who is coming. For a deeper look at pronouns and how they form possessives, see our guide on what is a pronoun.

Can I use an apostrophe to pluralize a single letter?

Yes — this is one of the few cases where an apostrophe in a plural is correct and necessary. When writing about individual letters, using an apostrophe before the s prevents confusion:

• Mind your p's and q's. (Without the apostrophe, ps and qs look strange.)
• She got straight A's this semester. (Though straight As is also widely accepted.)

For capital letters, the apostrophe is optional: the 1980s and three MBAs are clear enough without one. Use your judgment based on readability.

How do I handle possessives with inanimate objects?

English allows possessive apostrophes with inanimate objects, and this is perfectly standard: the car's engine, the table's surface, the city's budget. There is no rule that restricts the possessive apostrophe to living beings. That said, some writers prefer rephrasing with "of" for objects (for example, "the engine of the car"), particularly in formal writing. Either form is grammatically acceptable.

How can I catch apostrophe errors in my writing?

Reading your work aloud helps because you will hear when a word sounds like a contraction but is functioning as a possessive pronoun (or vice versa). For a more systematic check, our punctuation checker scans your text for apostrophe errors: misplaced apostrophes in plurals, missing apostrophes in contractions, and the common its/it's and your/you're mix-ups, and flags them in seconds. You can also run the text through our grammar checker for a full review of sentence-level issues alongside punctuation.