The apostrophe has exactly two jobs: showing possession and marking a contraction. Nearly every apostrophe mistake happens when writers forget this and start sprinkling them onto plain plurals. Learn the two real jobs and the mark stops being confusing.
Possession: whose is it?
For a singular noun, add 's: "the writer's laptop," "the dog's lead." For a plural noun that already ends in s, add just an apostrophe: "the writers' deadline," "the dogs' leads." For a plural that doesn't end in s, treat it like a singular: "the children's books," "the people's choice." The test is simple: find the noun that owns the thing, check whether it already ends in s, and apply the rule accordingly.
Contractions: something is missing
An apostrophe in a contraction marks where letters have been dropped: "it's" stands for "it is" or "it has," "don't" stands for "do not," "they're" stands for "they are." The single most common apostrophe error in English comes from confusing "it's" with "its." Remember: "its" is a possessive pronoun, like "his" or "her" — and you'd never write "her's" or "his's." No possessive pronoun takes an apostrophe. "It's raining" (it is raining) but "the cat licked its paw" (belonging to it).
Where apostrophes don't belong
Plurals never take an apostrophe just for being plural. "Banana's for sale" is wrong; it should be "bananas for sale" — unless you mean something belonging to a single banana, which is unlikely. This mistake is common enough to have its own nickname, the "greengrocer's apostrophe," precisely because it shows up so often on shop signs.
- Possessive singular: add 's — the client's brief.
- Possessive plural ending in s: add ' only — the clients' briefs.
- Contraction: apostrophe replaces missing letters — you're, it's, don't.
- Plain plural: no apostrophe, ever — laptops, apples, ideas.
When in doubt, ask yourself two questions: is something being owned, or are letters being dropped? If the answer to both is no, leave the apostrophe out.
