Major Vowel Harmony in Turkish

Major Vowel Harmony (Büyük Ünlü Uyumu or backness harmony) is the foundation of Turkish phonology. Vowels are partitioned into two strict classes based on the tongue's position: back vowels (kalın ünlüler: a, ı, o, u) and front vowels (ince ünlüler: e, i, ö, ü). When appending any two-fold grammatical suffix (conventionally denoted with capital -A or -E), the vowel in the suffix must match the class of the preceding syllable.

If the preceding vowel is back (a, ı, o, u), the suffix adopts a: araba (car) becomes arabalar (cars) and okul (school) becomes okulda (at school). If the preceding vowel is front (e, i, ö, ü), the suffix takes e: ev (house) becomes evler (houses) and göz (eye) becomes gözler (eyes). Compound nouns (karabiber) and foreign loanwords (kitap, otobüs) may violate internal harmony inside their stem, but any suffix added to them strictly conforms to the word's final syllable (kitap-lar, otobüs-te).

Learners frequently make mistakes by looking at the first syllable instead of the last, or by applying a single memorized suffix form regardless of harmony (such as saying evlar instead of evler). Another subtle trap involves Arabic/French loanwords ending in a palatalized consonant, where an apparent back vowel takes a front suffix (e.g., saat → saatler, rol → roller). Always inspect the final vowel to determine the correct harmonic form.