It’s helpful to know what a diphthong is first.
A diphthong is essentially a ‘glide’ from one vowel to another within one syllable. Consider the word ‘here’. If you slow down the pronunciation and break it down to each unit, you will get
hee-er
But normally you don’t pronounce ‘here’ as two distinct syllables, just one. “here”. Consider your mouth/tongue position. Try pronouncing “here” super slow, you’ll notice that your mouth/tongue’s position is different at the start of the word “hee” (tongue slightly more forward) and the end “er” (tongue further back). Your mouth/tongue slowly transitions from one position to another.
A triphthong is just a diphthong except instead of gliding over two vowels, it glides over three.
Consider the word “fire”. if you break it down and speak super slow, you’ll get
fa-ee-er
Fa. Ee. Er. Now if you say it all really fast, you just get “fire” as one syllable. That’s basically it.
Latest Answers