Pinyin Lessons Study Material GoodChinese
y is special sign in Chinese Pin-Yin, it can't form syllable alone. It sometimes expresses I and ü.
In general, it always appears in some Pin-Yin joinder form of standing as a syllable alone.
For example: The vowel ü and i are all only one Pin-Yin characted. When standing as a syllable as a syllable alone, they should be added y before them. Their forms are [yi],[yu] (erase two dot upon ü).
When [ia], [ie],[ian] etc. Compound finals forms syllable alone, I should be written y ,so their forms are [ya], [ye], [yan].
[iu] is a special compound final, when it forms syllables alone, is written as [you].
When y express ü, different from y express I, should add y before ü, meantime erase two dot rather than replace y.
Same as y, w also special sign, can't form syllable alone.
It only expresses u, and appears in some Pin-Yin joinder of standing as a alones.
The vowel u can only become one Pin-Yin character in Chinese, when it forms syllable alone should add w before it, becomes [wu].
When [ua],[uai],[uo] etc. Compound vowles form syllable alone, chang u to w, are writted as [wa],[wai],[wo].