Webster 1913 Edition
ðīn, originally gen. of
ðū, thou; akin to G.
þinn, possessive pron.,
þīn, gen. of þū thou, Goth.
þeins, possessive pron.,
þeina, gen. of
Thou, and cf.
A form of the possessive case of the pronoun thou, now superseded in common discourse by your, the possessive of you, but maintaining a place in solemn discourse, in poetry, and in the usual language of the Friends, or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 1828 Edition
THINE, pronominal adj. Thy; belonging to thee; relating to thee; being the property of thee. It was formerly used for thy, before a vowel.
Then thou mightest eat grapes thy fill, at thine own pleasure. Deut.32.
But in common usage, thy is now used before a vowel in all cases.
The principal use of thine now is when a verb is interposed between this word and the noun to which it refers. I will not take any thing that is thine. Thine is the kingdom, and the power, and the glory.
In the following passage, thine is used as a substitute for thy righteousness.
I will make mention of thy righteousness, even of thine only. Ps.71.
In some cases, it is preceded by the sign of the possessive case, like nouns, and is then also to be considered as a substitute.
If any of thine be driven out to the utmost parts of heaven-- Deut.30.
It is to be observed that thine, like thou, is used only in the solemn style. In familiar and common language, your and yours are always used in the singular number as well as the plural.