A person has 13 vowels, including 9 diphthongs and 4 tri-vowels:

Nine binary vowels: ai, ei, ao, ou, ia, ie, ua, uo, ü e;

Four triplet vowels: iao, iou, uai, uei；;

Extended data

Diphthongs is divided into pre-voiced vowels and post-voiced vowels, and triplet vowels are middle-voiced vowels:

① Compound vowels have four vowels: ai, ei, ao, ou?

② There are five vowels with polyphony: ia, ie, ua, uo and ü e. ..

③ There are four vowels with central polyphony: iao, iou, uai and uei.

References:

Baidu encyclopedia-vowels