tomparker OP t1_jdmizrg wrote

Brilliant. I’m going to see if I can fit this on a plastic label called edits

Use thy where you would use your and thine where you would use yours. BUT: if the noun placed after thy begins with a vowel sound, use thine instead: thy book, but thine eyes. Archaically, the same was done with my and mine, but this is no longer common usage outside of some poetic use.