Glossary · Sounds and phonemic awareness
What is a diphthong?
Definition
A diphthong is a vowel sound that glides from one position to another within one syllable, as in the oi of coin and the ou of cloud.
Say coin slowly and feel your mouth move. It starts near /o/ and slides toward /ee/. That glide is what makes a diphthong. The two main ones taught in phonics are /oi/ (spelled oi or oy) and /ou/ (spelled ou or ow).
Position helps with spelling. Oy and ow usually sit in final position (boy, cow), while oi and ou come in the middle (coin, loud). That rule covers most of the words students meet.
The word ow is a trap. It spells /ou/ in cow but long o in snow, so students need both and a habit of trying the other sound if the first one doesn't make a real word.
In a lesson
Put boy, coin, cow and loud on cards. The student reads each one and sorts by sound, then sorts again by where the spelling sits in the word.
Examples
Each word with its spelling units, one per sound.
- coinc·oi·n
- joinj·oi·n
- enjoye·n·j·oy
- sounds·ou·n·d
- groundg·r·ou·n·d
Words come from our lexicon, checked against a pronouncing dictionary. Words a student sees in our assessments are left out.
Why does this matter for the record?
Track ow carefully. Students who read it as long o everywhere need a note, because the error shows up in decodable text for months.
Rate each skill as you teach it
Needs support, Developing, Secure. The rating schedules the review and builds the report.