Vowel harmony

Definition
Vowel harmony is an assimilation process involving vowels of different syllables.

Example
In Turkish, the vowels of a suffix that are [+high] assimilate to the vowel of the stem with respect to the features [back] and [round]:

ev	- evim	'my house'	göz	- gözüm	 'my eye' gul	- gulum	'my rose'	basj	- basjim 'my head'

Links

 * Utrecht Lexicon of Linguistics