When does the y have a long i sound?

It usually has a long I when preceded by a consonant (by, my, nylon, python) and in a stressed syllable. In Words with single F-Y it is always a long I sound, and in Words made with the Word BY.

When paired with a vowel (A, E, O) the Y forms a diphthong sound (AY=A EY=A or E, OY= OI). With U, it may be an I sound (buy, guy) or an E (soliloquy).

Examples of Y as I:

fly, cry

bylaw, hereby

dye, lye, rye

defy, rely

buy, guy