18 vowels are ai, ei, ui, ao, ou, iu, ie, ve, er, an, en, in, un, vn, ang, eng, ing, ong.

A vowel is a vowel composed of one vowel, also known as a vowel. A compound vowel is a vowel composed of two or three vowels. This polyphony is not a simple addition of two vowels or three vowels, but a new and fixed phonetic group, which has the same effect as the unit rhyme in the mouth and ears and should be regarded as a phonetic whole.

Extended data:

Six skills of memorizing single vowels:

Open mouth a a a, round mouth o o o, flat mouth e e e e e e.

Teeth arranged neatly, ii ii, mouth protruding u u u, mouth round.

The doctor checked, the cock crowed and the white goose swam.

Clothes hang on the wall, ii ii, crows build nests, fish spit bubbles.

(bosom friend) One level, two liters, three turns and four falls.

Monovowel, the cutest, with a tuning hat on his head. A has a, oe has no a.

I and u are marked side by side, and the emphasis on I is removed. Needless to say, single vowels never have tones.