Second Grade English: Diphthongs & Glided Vowels

When you speak, some vowel sounds stay in one fixed mouth position from start to finish, while others embark on a swift journey across your vocal tract. These special moving sounds are known as diphthongs or glided vowels. The word diphthong comes from an ancient Greek term meaning "two sounds" or "two voices." In this chapter, you will explore how diphthongs work, discover the physical movement of your lips and jaw as you pronounce them, and master the two premier diphthong sound families of second grade: the /ɔɪ/ sound and the /aʊ/ sound.

The Science of a Glided Vowel

A diphthong is not simply two letters printed next to each other; it is a single syllable vowel sound that begins at one vowel position and glides smoothly into another.

+-----------------------------------------------------------------+
|                   ANATOMY OF A GLIDED VOWEL                     |
+-----------------------------------------------------------------+
|                                                                 |
|   Starting Sound                 Finishing Sound                |
|   [ Open Mouth Position ]  --->  [ Closed Smile Position ]      |
|                                                                 |
|   Example: Pronouncing the word "COIN"                          |
|   Start at /ɔ/ (round lips)  --> Glide into /ɪ/ (narrow lips)   |
|                                                                 |
+-----------------------------------------------------------------+

Pure Vowels vs. Glided Diphthongs

In a pure vowel sound like the short o in hot, your tongue, lips, and jaw remain perfectly still while making the sound. Say hot slowly: your mouth does not move at all during the vowel. Now say coin or shout slowly: you can physically feel your jaw rise and your lips change shape midway through the vowel. That physical shift is the hallmark of a true diphthong!

The Two Master Diphthong Sound Families

In second grade, your primary focus is mastering the two most prominent diphthong sound families in English.

+-----------------------------------------------------------------+
|                THE TWO MASTER DIPHTHONG FAMILIES                |
+-----------------------------------------------------------------+
|  Diphthong Sound | Spellings | Starting Position | Ending Target|
+------------------+-----------+-------------------+--------------+
|  /ɔɪ/ ("oy")     | oi, oy    | Round open lips   | High smile   |
|  /aʊ/ ("ow")     | ou, ow    | Open dropped jaw  | Tight puckered|
+------------------+-----------+-------------------+--------------+

The /ɔɪ/ Family: The oi and oy Spellings

This lively sound begins with rounded lips producing an "aw" sound and glides upward into a high "ee" sound. The oi spelling is used inside syllables: point, spoil, noise, choice, voice, and soil. The oy spelling is used at the end of syllables: boy, toy, enjoy, loyal, voyage, and annoy.

The /aʊ/ Family: The ou and ow Spellings

This dynamic sound starts with an open jaw saying "ah" and glides swiftly into a rounded puckered mouth saying "oo". The ou spelling appears inside words: shout, loud, couch, pounce, bounce, hound, and mouth. The ow spelling appears both inside words (clown, crowd, brown, town) and at the end of base words (cow, how, now, plow).

Kinesthetic Reading: Feeling the Glide

To become aware of diphthongs, you can use your fingers to feel the movement of your facial muscles.

+-----------------------------------------------------------------+
|                     THE TWO-FINGER JAW TEST                     |
+-----------------------------------------------------------------+
|  1. Place two fingers gently on your chin.                      |
|  2. Say the word "COT" (pure short o).                          |
|     Notice your chin stays down in one place.                   |
|  3. Now say the word "COW" (diphthong ow).                      |
|     Notice your chin rises and moves as you finish the sound!   |
+-----------------------------------------------------------------+

Why Diphthongs Matter for Spelling

When spelling words with diphthongs, many young writers make the mistake of leaving out the second letter because the sound feels like one continuous movement. Remembering that every diphthong is a glide made of two letters working as a team ensures you include both vowel letters every time.

Decodable Story: The Royal Owl

Practice reading this short narrative containing multiple diphthongs.

+-----------------------------------------------------------------+
|                   STORY: THE ROYAL OWL                          |
+-----------------------------------------------------------------+
|  A loyal royal boy had a brown owl.                             |
|  The owl made a loud noise when it flew south.                  |
|  It found a shiny gold coin on the damp ground.                 |
|  The boy felt great joy and gave the owl a soft toy.            |
+-----------------------------------------------------------------+

Practice Exercises

Exercise 1: Read the following four words and identify the diphthong spelling used in each: crowd, voice, pouch, destroy.

Exercise 2: Explain in your own words how your mouth moves differently when you say a pure vowel sound versus a diphthong.

Exercise Solutions

Solution to Exercise 1: In the word crowd, the diphthong spelling is ow. In voice, the diphthong spelling is oi. In pouch, the diphthong spelling is ou. In destroy, the diphthong spelling is oy.

Solution to Exercise 2: When saying a pure vowel sound, your lips, jaw, and tongue stay in one steady position throughout the sound. When saying a diphthong, your mouth physically moves and shifts, beginning in an open position and gliding into a narrower position before the vowel sound ends.