Their pron. & a.  The possessive case of the personal pronoun they; as, their houses; their country.
  Note: ☞ The possessive takes the form theirs (░) when the noun to which it refers is not expressed, but implied or understood; as, our land is richest, but theirs is best cultivated.
  Nothing but the name of zeal appears
  'Twixt our best actions and the worst of theirs.   --Denham.
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