A diphthong is when we have two short vowels together in the same syllable and they form an individual sound
[aɪ]
FLY, BUY, HEIGHT, LIE
[eɪ]
STAY, WAIT, WEIGHT ..
[ɔɪ]
VOICE, OIL, BOY.
[ɪə]
BEER, HEAR, HERE
[eə]
BEAR, HAIR, PEAR, PAIR.
[aʊ]
TOWN, ROUND.
[əʊ]= [oʊ]
PHONE, LOAN, GO, BLOW
.
*[ʊə]= [ɔː]
SURE, POOR.