Apostrophes
The apostrophe has exactly two uses in English: contractions and possession. Knowing which is which — and when not to use one — prevents the most common punctuation errors.
Use 1: Contractions
An apostrophe replaces missing letters when two words are joined into one shorter form.
| Full form | Contraction | Full form | Contraction |
|---|---|---|---|
| I am | I'm | do not | don't |
| she is / she has | she's | does not | doesn't |
| they are | they're | did not | didn't |
| we will | we'll | will not | won't |
| it is / it has | it's | cannot | can't |
| I would / I had | I'd | should not | shouldn't |
I'm not sure where she's gone. They're coming at six.
It's raining outside. (= It is raining)
We won't be late. She doesn't know.
Use 2: Possession (possessive apostrophe)
An apostrophe + s shows that something belongs to someone.
| Rule | Example |
|---|---|
| Singular noun → add 's | the dog's lead, Maria's book, the teacher's desk |
| Plural noun ending in -s → add ' only | the students' results, the girls' room, my parents' car |
| Irregular plural not ending in -s → add 's | the children's toys, the men's team, the women's league |
| Singular proper noun ending in -s → add 's (standard) | James's book, Charles's coat |
This is Tom's car. (singular — Tom owns the car)
The students' essays were excellent. (plural — many students)
The children's playground is closed. (irregular plural)
it's vs. its — the most common mistake
it's (with apostrophe) = it is or it has: It's raining. It's been a long day.
its (no apostrophe) = belonging to it: The cat licked its paw. The company lost its contract.
Never use apostrophes for plurals: apple's ✗ → apples ✓ CD's ✗ → CDs ✓ the 1990's ✗ → the 1990s ✓. An apostrophe does not make a word plural. This is sometimes called the "greengrocer's apostrophe" and is one of the most frequent punctuation errors.
its/it's test: If you can replace the word with "it is" or "it has" and the sentence still makes sense, use it's (with apostrophe). If not, use its. Try: "The cat licked [it is] paw" — doesn't work → use its.