Diphthongs oi and oy

Read the gliding vowel sound spelled oi and oy, and know where each spelling goes.

A diphthong is a vowel sound that glides from one position to another in your mouth. Say 'boy' slowly and feel your mouth move from 'oh' toward 'ee'. That gliding sound is spelled two ways: 'oi' and 'oy'. The rule for choosing is about position. 'Oi' is used in the middle of a syllable: coin, point, avoid, moisture.

'Oy' is used at the end of a syllable or word: boy, enjoy, toy, and in syllables like 'roy-al' and 'voy-age'. So if you hear the sound at the end, spell it oy. If you hear it in the middle, followed by a consonant, spell it oi. Read: 'The loyal boy pointed to the shiny coin in the soil. '

• 1A diphthong is a gliding vowel sound.
• 2oi in the middle of a syllable (coin).
• 3oy at the end of a syllable (boy, roy-al).