oi diphthong
Rule Core
The oi diphthong is pronounced /ɔɪ/, a smooth glide from a rounded back vowel to a high front vowel. It is most commonly spelled oi or oy, and the sound remains stable across word positions.
Articulation Guide
Start with /ɔ/: lips rounded, tongue back. Glide quickly to /ɪ/: lips relax, tongue moves forward and slightly up. The motion is continuous and brief.
Word Analysis
- adjoin /əˈdʒɔɪn/: oi carries the stressed vowel.
- appoint /əˈpɔɪnt/: oi appears medially with a crisp glide.
- appointment /əˈpɔɪnt.mənt/: the oi sound remains unchanged despite added syllables.
Pitfall Avoidance
Do not lengthen the vowel or reduce it to /o/. The key feature is the vowel glide, not vowel duration.
Phonics Breakdown
Round lips for /ɔ/, then glide forward and up to /ɪ/ in one motion
Sound Reference
- Practice the glide /ɔ/→/ɪ/ slowly before speeding up
- Contrast coin vs. cone to feel the difference
Common Mistakes
Reading oi as a long /oː/
Reducing the glide in longer words
Example Words
All Words (42)
adjoin appoint appointment avoid boil boiler choice coil coin coinage disappoint disappointment embroidery employee employment exploitation foil join joint jointly moist moisture noise oil oily point pointed pointless poise poised poison poisoning poisonous rejoice rejoicing soil standpoint tinfoil toil toilet viewpoint void