Their (?), pron. & a. [OE. thair, fr. Icel. þeirra, þeira, of them, but properly gen. pl. of the definite article; akin to AS. ðāra, ð&aemacr;ra, gen. pl. of the definite article, or fr. AS. ð&aemacr;ra, influenced by the Scandinavian use. See That.] The possessive case of the personal pronoun they; as, their houses; their country.

&fist; 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.

Their (?), pron. & a. [OE. thair, fr. Icel. þeirra, þeira, of them, but properly gen. pl. of the definite article; akin to AS. ðāra, ð&aemacr;ra, gen. pl. of the definite article, or fr. AS. ð&aemacr;ra, influenced by the Scandinavian use. See That.] The possessive case of the personal pronoun they; as, their houses; their country.

&fist; 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.

• belonging to them.
       They will meet tomorrow at their convenience.
       This is probably their cat.
  
• belonging to someone of unknown gender
       Everyone must understand their feelings.