The Apostrophe Rules That Actually Cause Trouble

The apostrophe does two jobs: it marks possession, and it marks missing letters. Almost every error comes from confusing those two, or from adding one where neither applies.

The one that matters most

Its is possessive. It’s means it is or it has.

This looks backwards, and there is a reason. Possessive pronouns never take apostrophes: his, hers, ours, theirs, yours, whose. Its belongs to that family. The apostrophe in it’s is doing the other job entirely — standing in for the missing i in is.

The test: expand it to it is. If the sentence survives, use it’s. If not, use its.

The same test settles your/you’re, their/they’re and whose/who’s. All four are the same problem wearing different clothes.

Names ending in s

Genuinely disputed, and both answers are defensible.

Chicago: add ‘s regardless. James’s book, Dickens’s novels.
AP: apostrophe only. James’ book, Dickens’ novels.

A useful tiebreaker: write what you say. If you pronounce the extra syllable — Jamesiz book — write James’s. If you do not, write James’. Most speakers do pronounce it, which is why Chicago’s rule tends to feel more natural.

Plural possessives

Form the plural first, then add the apostrophe. Doing it in that order removes almost all the difficulty:

One dog → the dog’s bone
Several dogs → the dogs’ bones
One child → the child’s toy
Several children → the children’s toys — because children is already plural, the ‘s goes on the end as normal

Irregular plurals — men, women, people, mice — all behave like children. The women’s team, never the womens’ team.

Where it does not belong

Ordinary plurals. This is the famous one:

Wrong: Fresh apple’s, Open Sunday’s, The Smith’s
Right: Fresh apples, Open Sundays, The Smiths

To make a family name plural, add s — or es if it ends in s, x, z, ch or sh. The Smiths, the Joneses. To make it possessive and plural: the Joneses’ house.

Decades. The 1990s, not the 1990’s. The apostrophe belongs only in the shortened form: the ’90s, where it marks the missing 19.

Acronyms. Three CEOs, not three CEO’s.

The one exception worth knowing

Single letters take an apostrophe in the plural, because the alternative is unreadable: mind your p’s and q’s, dot the i’s. Without it, as and is become other words entirely.

That is the whole exception. It does not extend to anything else.