The Difference Between Diphthongs And Digraphs
By Linda Farrell
The terms digraph and diphthong are common terms in the reading world. At workshops on spelling or phonics, I often find that many people are confused about the difference between the two terms.
The clear difference is that digraphs are letters and diphthongs are sounds. The morphemes (meaningful word parts) in each word help us remember their meanings. Both words are derived from Greek. The first morpheme di in both words means “two.” The morpheme graph means written, making the word digraph refer to something written that has two parts. The morpheme phthong means “sound”, making the word diphthong refer to a sound that has two parts. If you understand the meaning of the morphemes in each word, you will never confuse them again.
A digraph is two letters that spell one sound. Digraphs that spell consonant sounds include the letter pairs sh, ch, th, wh, ck, ph, ng. Digraphs that spell vowel sounds include the letter pairs ai, ay, ee, ea, ie, ei, oo, ou. ow, oe, oo, ue, ey, ay, oy, oi, au, aw. The important thing to remember is that a digraph is made of two letters, and although the letters spell a sound, the digraph is the two letters, not the sound.
A diphthong is a special kind of vowel sound. Most vowel sounds in English are made with the mouth in one position and with one pure sound. These vowel sounds are called monophthongs (mono meaning “one” and phthong meaning “sound”). A diphthong is one vowel sound formed by the combination of two vowel sounds. A diphthong begins as one vowel sound and moves toward another, such as the vowel sounds in coin or loud. Diphthongs can be contrasted with two monophthong vowel sounds together that form two syllables, such as in chaos, triage, or violin.1
When teaching reading, the two vowel sounds most commonly identified as diphthongs are /oy/ and /ow/. The most common spellings for the vowel sound /oy/ are oy (toy) and oi (void), and the two most common spellings for /ow/ are ow (cow) and ou (cloud). The fact that these two diphthongs are usually spelled with digraphs may explain the confusion between the terms.
1 To feel the difference between a monophthong and a diphthong, you can put an index finger on either side of your mouth. Say the vowel sound /ă/ and your fingers will stay in the same position because your mouth doesn’t move. The same thing happens with most vowel sounds. However, if you say the vowel sounds /oy/ or /ow/, your fingers will move because your mouth moves from one vowel sound to another. Two other diphthongs in American English are long i (/ī/) and long a (/ā/), which are always identified as diphthongs by linguists but not often by reading teachers. Both these vowel sounds pass the diphthong test, which is movement of a part of the mouth, generally the tongue or lips, while saying a vowel sound. Other diphthongs exist in various dialects and other languages.
Very good explanation by Lynda Farell about difference between dipthongs and digraph. Thanks
Oh my goodness! Thank you! I have two different phonics books (Modern Curriculum Press and Scholastic) and they had me terribly confused with their conflicting descriptions.
Lynda Farell has written an explanation that is clear, concise, and firmly rooted in knowledge. I’m so pleased I found this newsletter!
A diphthong is written as a digraph?
That’s not what I understood from above. Often it is two letters but it doesn’t need to be. See example of long /i/ and long /a/
Great explanations. I do wonder, however, why the written versions of dipththongs are considered digraphs and not blends. Two letters combined where one sound is heard is a digraph. Two or three letters combined where all letter sounds are heard is a blend. In diphthongs two letter sounds can be distinguished.
Diphthongs make one single sound. That is different than a blend.
Excellent explanation of the distinction! Thank you for sharing in a manner so easy to understand.
Thank you! This makes so much sense now.
thanku so much it was too much helpful!
Thanks. Very clearly explained.
A very clear and crisp explanation. Thank you.
Thank you Ms. Farrell for explaining the difference between ‘digraph’ and ‘diphthong’. You cleared the mystery! I was having the hardest time ever understanding the difference. I deeply appreciate that you explained ‘monophthongs’ a word that I had never heard before but was extremely important to know.
Hi all,
I have a question. Is there a way to learn and master 44 sounds of English and then be able to read and categorize words based on that knowledge?
Thanks:)
I would like the answer to that very question too.
Wonder if the problem comes with the many ways we can spell those 44 sounds.
This makes so much sense! Remembering to break the words into their morphemes and knowing their original meanings is so helpful. Thanks for taking the time to write this.
Wow clear explanation
In phonetics we were taught that words like “apple” and “act” have the sound combination “ae” and our materials called it a diphthong. Our phonetics differentiated between broad “a” tomato (Boston), long “a” tomato (most U.S.A.), and diphthong “ae” apple.
I still confused why long a and long i are considered diphthongs? Using the two-finger test, I can’t make it work for me.
Well-explained, clear and concise. Thank you for the article; it has definitely helped to rid of confusion over the two terms.
wonderful explanation. Thank you for clarifying my doubts.
Great description. One critique is that everyone should use IPA when describing sounds. When I see something in phonemic slashes like /ā/ and /ī/, I think, oh, /a:/ like father. But you mean /ei/ and /ai/.
I know it stems from a desire to hang closer to English orthography, but English orthography is royally messed up from the Great Vowel Shift and using pseudo-phonetic spelling like this is way more confusing than it needs to be.
I’d love to hear more how “oi” in coin is a dipthong but the “oy” in toy is a digraph when it’s the exact same 2 sounds.