thy
det.det. an old word for 'your'. You use it when talking to one person you know well, mostly in old poems or religious books.
det. the archaic second-person singular possessive determiner. Used historically in informal or intimate contexts, though now restricted to liturgical, poetic, or highly stylised registers.
Honor thy father and thy mother.
The poet wrote of the sun's rays warming thy face as you wake.
In the sonnet, the speaker addresses a beloved directly, using thy to establish an intimacy that the more formal 'your' would fail to convey to a contemporary audience.
From Middle English þi, apocopated variant of þin, from Old English þīn, from Proto-West Germanic þīn, from Proto-Germanic þīnaz, from Proto-Indo-European téynos (“thy; thine”), from Proto-Indo-European túh₂ (“thou”). See thou.
Used before words starting with a consonant sound; 'thine' is used before vowel sounds or as a possessive pronoun.
thy eyesthine eyesHistorically, 'thy' is used before consonants, while 'thine' is used before vowels, similar to the rule for 'a' and 'an'.