A language with a triple vowel harmony distinction is Manchu. In this language there are three "strong" vowels,
a, e, o and two "weak" ones,
i, u. The vowel harmony in Manchu is a bit tricky, in a word a "strong" vowel can be followed by the same "strong" one or by any of the "weak" ones, but a "weak" vowel can be followed by a "weak" vowel or by
a, but never by
o. That is, three sets of vowels are possible within a word:
- a, i, u
- e, i, u
- o, i, u
The 3rd row can also be like that:
o, o, ..., i/u ..., a, i, u.
That is, the 3rd row can change into the 1st one, so we can say the vowel harmony in Manchu has a stair-step character.
According to that vowel harmony, suffixes in Manchu are of the two kinds:
- some have a "weak" vowel and they never change, since they can be added to roots that have any vowels:
-mbi - present tense,
-fi - participle: "arafi" (having written), "genefi" (having gone), "songofi" (having wept), "arabumbi" (make write), "genebumbi" (make go);
- others have three variants, with each of the strong vowels:
-sa/-se/-so - plural noun suffix,
-ha/-he/-ho - past participle: "araha" (wrote), "genehe" (went), "songoho" (wept).
The change of the 3rd row into the 1st one can be illustrated by "songobuha" (made weep), where the
u in the causative suffix
-bu changes the 3rd
o row into the 1st
a row, so
-ho is added.
В. Аврорин, Грамматика маньчжурского письменного языка, СПб, "Наука", 2000