theirs
pron.pron. the thing or things that belong to a specific group of people. You use it to replace a noun so you do not have to repeat it.
pron. the third-person plural possessive pronoun, used to refer to things belonging to or associated with two or more people. Functions as a nominal substitute to avoid repetition of a noun phrase.
I have my keys, but they forgot theirs.
Our garden is quite small, but theirs is large enough for a swimming pool.
While our research focused on urban development, theirs examined the impact of rural migration on local economies over the same ten-year period.
From Middle English theires, attested since the 1300s. Equivalent to their + -s (compare -'s); formed by analogy to his. Displaced theirn (from Middle English theiren, formed by analogy to mine, thine) in standard speech.
Functions as a predicative or independent possessive; it never precedes a noun.
their'stheirsPossessive pronouns like 'theirs', 'ours', and 'yours' never take an apostrophe.