oi/oy diphthong

Core Rule

oi/oy represents the diphthong /ɔɪ/, a smooth vowel glide found in English. The sound stays the same, but spelling position differs: oi appears in the beginning or middle of words, while oy is typically used at the end.

Articulation Guide

Start with a rounded, back vowel /ɔ/. The lips are slightly rounded and the tongue is low-back. Glide quickly to /ɪ/, moving the tongue forward and relaxing the lips. Airflow is continuous with no break.

Word Deployment

oi: coin, voice, point, soil. oy: boy, toy, enjoy, deploy. In deploy, the oy occurs at the end of a stressed syllable, keeping the same /ɔɪ/ sound.

Pitfalls

Do not pronounce oi/oy as a long /o/ or confuse it with ou/ow (/aʊ/). Spelling changes do not affect pronunciation.