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;
☞ The possessive takes the form theirs (&unr_;) when the noun to which it refers is not expressed, but implied or understood; as, our land is richest, but theirs is best cultivated. [ 1913 Webster ]
Nothing but the name of zeal appears
'Twixt our best actions and the worst of theirs. Denham. [ 1913 Webster ]