theirs
- 1The form of they used on its own to mean the thing or things belonging to them.
These tickets are ours, and the ones by the door are theirs.
Our garden flooded last spring, but theirs stayed dry.
Note
A pronoun that stands alone where their would need a noun after it: the luggage is theirs, but it is their luggage. Its -s came in Middle English by analogy with his, and it pushed an older theirn, modeled on mine and thine, out of standard speech. It also follows of, as in Henry James's "a good friend of theirs in London" (1878), and it is spelled without an apostrophe.
- 2The house or home belonging to them.
After the movie, everyone headed back to theirs for coffee.
I left my coat at theirs and had to go back for it.
Note
Here the ordinary possessive carries an unspoken home. It turns up after words of place and motion: over to theirs, back to theirs, at theirs. Keep it for conversation and relaxed writing. In formal prose, their place or their house says the same thing more safely.
Use it in a sentence
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Origin
From Middle English theires, attested since the 1300s, equivalent to their plus -s (compare the possessive -'s) and formed by analogy to his. It displaced theirn (from Middle English theiren, formed by analogy to mine and thine) in standard speech.