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What Is an American English Diphthong? Definition and Explanation

written by: Linda M. Rhinehart Neas • edited by: Elizabeth Stannard Gromisch • updated: 12/27/2013

When asked, "What is a diphthong?", many people are lost for an answer. Learning the meaning of the word, where diphthongs are found, and how to use them will aid ESL learners in understanding American English. Diphthongs are one of those parts of language that simply must be memorized.

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    What Is a Diphthong

    The word diphthong comes from the Greek diphthongos which means two tones or two sounds. The dictionary defines a diphthong asEnglish Language Arts 

    "an unsegmentable, gliding speech sound varying continuously in phonetic quality but held to be a single sound or phoneme and identified by its apparent beginning and ending sound, as the oi- sound of toy or boil."

    In English, we have many words with gliding vowels or diphthongs, which means that the words have two vowel sounds in one syllable. Most linguists agree that there are eight diphthongs in the English language (although some argue for as few as three). The most common diphthongs in American English are said to be /ow/, /ou/, /oy/ and /oi/ as in row, round, joy and join. Diphthongs, however, do not always have two written vowels side-by-side in the syllable that makes the word. For instance, five has the diphthong /ai/.

    In teaching diphthongs, linguists suggest that we think of the vowel sound moving from one vowel to another, thus "gliding" into the final sound. For instance, if we use the word hound, we hear what sounds like "ha" followed by "ou". The first sound flows into the final sound to create the word.

    Another consideration in teaching American English diphthongs is that of dialect. In various parts of the country, words are pronounced with diphthongs that are not heard anywhere else. For instance, in New England, the word hair is pronounced "hay-uh, rather than "hay-er."

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    How to Teach Them

    Teaching diphthongs can be a Pandora's Box for ESL teachers. By keeping the lessons as simple as possible, teachers can help students grasp the concepts without getting lost in the linguistics. Rather than confusing students with the complexities of phonetic symbology, use the actual vowels that are in the words to teach the diphthongs. Pronunciation of these words will be mastered by repeated vocalization rather than sight recognition. Sometimes, too, a foreign language shares a diphthong with English (such as the ai in the English five and the Spanish bailar) which makes teaching diphthongs a little easier.

    Diphthongs in American English are:

    (Please note that the diphthongs are shown first in parenthesis, then listed by sound are the variations of spelling for that diphthong, followed by word examples.)

    • (Iə) - /ee/, /ie/, and /ea/ as in deer, fierce, and beard
    • (eə) - /ai/, /a/, and /ea/ as in fair, care and pear
    • (ʊə) - /oo/, /ou/, /u/, and /ue/ as in poor, tour, plural and cruel
    • (eI) - /ey/, /ay/, /ai/, and /a/ as in they, play, pain and race
    • (aI) - /i/, /igh/ and /y/ as in idea, light and my
    • (ɔI) - /oy/, and /oi/ as in boy and join
    • (oʊ) - /ow/, /oa/ and /o/ as in show, load and go
    • (aʊ) - /ou/, and /ow/ as in sound and how

    As you can see from the list, while the sounds differ, many words have similar spelling, such as show and how or fair and pain. For this reason, it is important to teach with repeated vocalization, which will enable students initially to identify the words by their sound rather than their spelling.

    Some other tricks to teaching diphthongs include using rhyme. Begin with a common word such as boy. Have students brainstorm all other words they know that sound like boy. In addition, create an interactive word list on the wall where students can add words with diphthongs as they learn them. You can also give older students a clipping of text from a newspaper or magazine article on which they circle words they recognize with diphthongs. Have them underline words they are not sure of, which you will then discuss as a group. Finally, create worksheets as well as check online for printable versions of premade worksheeks for practice in identifying the various diphthongs.

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    An Ear for Diphthongs

    In discovering what a diphthong is, it is essential to concentrate on aiding students to develop listening skills that will help them identify words with diphthongs. Avoid teaching the phonetic symbolism for the diphthongs as that will confuse the students. Learning one language is difficult enough. Learning another in order to understand the initial language is counterproductive. Repeated speaking and listening enable students to grasp the words. Following the tips above, however, can make teaching American diphthongs to English language learners a fun and fruitful endeavor.


    • Sing Your Way through Phonics:
    • ESL Teachers Board - Diphthongs: