linguistic:voice_change
Vowel harmony

The principle of vowel harmony, which permeates Turkish word-formation and suffixation, is due to the natural human tendency towards economy of muscular effort. This principle is expressed in Turkish through three rules:

The second and third rules minimize muscular effort during speech. More specifically, they are related to the phenomenon of labial assimilation: if the lips are rounded (a process that requires muscular effort) for the first vowel they may stay rounded for subsequent vowels. If they are unrounded for the first vowel, the speaker does not make the additional muscular effort to round them subsequently.

Grammatical affixes have "a chameleon-like quality", and obey one of the following patterns of vowel harmony:

Practically, the twofold pattern (also referred to as the e-type vowel harmony) means that in the environment where the vowel in the word stem is formed in the front of the mouth, the suffix will take the e-form, while if it is formed in the back it will take the a-form. The fourfold pattern (also called the i-type) accounts for rounding as well as for front/back. The following examples, based on the copula -dir (" is"), illustrate the principles of i-type vowel harmony in practice: Türkiye' dir ("it is Turkey"), kapı dır ("it is the door"), but gün dür ("it is the day"), palto dur ("it is the coat").