I'm having some trouble figuring out which is the vowel proper in each word. Can anyone explain how it is determined?

Question

anonymous · Answer

From the "sounds and symbols 1" reading --> 'As a rule of thumb, look to see if the first of two vowel letters is a possible medial (i, u, ǜ); if it is, then the next vowel letter is the core vowel, and that gets the tone mark; if not, then the first gets it: iè, ǎo, ué, ōu, iào.'

Does this help explain it?

anonymous · Answer

It helped a little. Is is something like which vowel comes first in the alphabet?

anonymous · Answer

No. It means that if the letter after the beginning sound is i, u, or ǜ, then it is not the vowel proper. So in dào, the a is the letter after the beginning sound, and it is the vowel proper because it is not i, u, or ǜ. For liù, because 'i' is the vowel after the beginning sound the next vowel must be the proper.

Which words are you having trouble with?