Understanding Diphthongs
A diphthong is a vowel sound that begins with one sound and then glides into another within the same syllable. These special vowel teams make a single sound that is different from their usual short or long vowel sounds.
- oi → coin
- oy → boy
- ou → out
- ow → cow
When vowels team up to make a new sound, think of them as “working together” to glide from one sound to another.
Pattern oi and oy
The diphthongs oi and oy make the /oi/ sound, like in coin or boy. The spelling oi usually appears in the middle of words, and oy usually comes at the end of words.
- coin (oi)
- boil (oi)
- toy (oy)
- enjoy (oy)
Remember: oi stays inside a word, while oy likes to play at the end!
Pattern ou and ow
The diphthongs ou and ow make the /ou/ sound, like in out or cow. They can sometimes make other sounds, but in first grade we focus on their most common /ou/ sound.
- out (ou)
- shout (ou)
- cow (ow)
- now (ow)
Think of the /ou/ sound as a surprised “ouch!”—both ou and ow can spell it.
Practicing Diphthongs in Sentences
Seeing diphthongs in sentences helps us learn how to read and understand them in real stories and passages.
- The boy has a toy coin.
- The cow is out in the field.
- She will enjoy a loud shout.
- He found a brown owl.
When you read, listen for how the vowel sound changes or “glides.” That’s what makes it a diphthong!