oi diphthong

Rule Core

The oi diphthong is pronounced /ɔɪ/, gliding from a mid-back rounded vowel to a high front vowel. Common spellings are oi (coin) and oy at word end (boy).

Articulation Guide

Start with rounded lips and a relaxed jaw, tongue slightly back; then glide forward and upward smoothly.

Examples

coin, oil, voice; final-position boy, enjoy. Stress does not change the vowel quality.

Pitfalls

Do not reduce it to /o/ or confuse it with oo/ou, which lack the forward glide.