Definition · Plain-language
Apostrophe
An apostrophe ( ’ ) is a punctuation mark with two main jobs: it shows possession (the dog’s lead) and marks missing letters in contractions (don’t).
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Showing possession
The apostrophe’s commonest job is to show ownership. For a singular noun, add ’s: "the author’s argument", "James’s car" (most modern British style guides add the s even after a final s). For a plural noun that already ends in s, add only an apostrophe: "the students’ results". For irregular plurals that do not end in s, add ’s as normal: "the children’s playground". The position of the apostrophe tells the reader whether one owner or several is meant — "the manager’s decision" is one manager, while "the managers’ decision" is several. Getting that placement right is one of the most useful punctuation skills in formal writing.
Marking contractions
The apostrophe’s second job is to stand in for letters that have been removed when two words are joined into a contraction. Do not becomes don’t, I am becomes I’m, they have becomes they’ve, and cannot becomes can’t. The apostrophe sits exactly where the missing letters were. The same logic explains the most confused pair in English: it’s means "it is" or "it has", with the apostrophe marking the gap, whereas its (no apostrophe) is the possessive. Contractions are normal in most writing, though some very formal academic styles prefer the full forms; either way, the apostrophe placement follows the missing letters.
When NOT to use an apostrophe
A frequent error is using an apostrophe to form a plural — the so-called greengrocer’s apostrophe, as in "apple’s for sale". Ordinary plurals take no apostrophe: apples, DVDs, the 1990s. Possessive pronouns also never take one: its, hers, ours, yours, theirs and whose are already possessive, so adding an apostrophe (it’s, your’s) is wrong. Decades and acronyms are pluralised without one too. The simplest check is to ask what job the apostrophe would do: if it is not marking possession or a missing letter, it should not be there. This single test prevents most apostrophe mistakes.
Key facts
At a glance
- Definition: a mark showing possession or omitted letters in a contraction
- Singular possessive: add ’s (the cat’s bowl)
- Plural possessive: add an apostrophe after the s (the cats’ bowls)
- Contractions: marks missing letters (do not → don’t)
- Never for: ordinary plurals (apples, not apple’s) or possessive pronouns (its)
- Watch: it’s = it is/has; its = possessive
Common misconceptions
What people often get wrong
Often heard: You add an apostrophe to make a word plural, as in "photo’s".
Actually: Ordinary plurals never take an apostrophe; the plural of photo is photos. The apostrophe is for possession or contractions, not for forming plurals.
Often heard: Possessive pronouns like "its" and "yours" need an apostrophe.
Actually: Possessive pronouns are already possessive and take no apostrophe: its, hers, ours, yours, theirs. The form it’s with an apostrophe means only "it is" or "it has".
Often heard: A singular name ending in s, like James, cannot take ’s.
Actually: Most modern style guides add ’s: "James’s book". Some traditional styles use just an apostrophe ("James’ book"); both are seen, but the key is to be consistent.
Going deeper
