Meaning of THEIRS in English

THEIRS

/ ðeəz; NAmE ðerz/ pronoun

(the possessive form of they ) of or belonging to them :

Theirs are the children with very fair hair.

It's a favourite game of theirs.

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WORD ORIGIN

Middle English : from their + -'s .

Oxford Advanced Learner's English Dictionary.      Оксфордский английский словарь для изучающик язык на продвинутом уровне.