morphology: vowels

A glide is i or u when followed by a nucleus and not followed by abother glide.

A diphthong is one of ai, au, ei, oi not followed by a glide.

A vowel is one of a, e, i, o, u not followed by a nucleus.

a is any number of commas (possibly none) and the character 'a' or 'A'.

e is any number of commas (possibly none) and the character 'e' or 'E'.

i is any number of commas (possibly none) and the character 'i' or 'I'.

o is any number of commas (possibly none) and the character 'o' or 'O'.

u is any number of commas (possibly none) and the character 'u' or 'U'.

y is any number of commas (possibly none) and the character 'y' or 'Y'.