Thine (?), pron. & a. [OE. thin, AS. &edh;in, originally gen. of &edh;u, &edh;&umac;, thou; akin to G. dein thine, Icel. þinn, possessive pron., þin, gen. of þ&umac; thou, Goth. þeins, possessive pron., þeina, gen. of þu thou. See Thou, and cf. Thy.]
A form of the possessive case of the pronoun thou, now superseded in common discourse by your, the possessive of you, but maintaining a place in solemn discourse, in poetry, and in the usual language of the Friends, or Quakers.
⇒ In the old style, thine was commonly shortened to thi (thy) when used attributively before words beginning with a consonant; now, thy is used also before vowels. Thine is often used absolutely, the thing possessed being understood.
© Webster 1913.