Although most aspects of Turkish grammar are quite formulaic and fairly regular, as is the case with most languages, you will find exceptions to many of its rules. Just as with English irregular past tense or irregular plurals, motivations for the “irregular” forms are only available in historical context and no discernible rules or patterns can be extracted by the current speakers. In other words, these exception have become lexical entries in speakers’ minds and simply learned through rote memorization. Furthermore, as you will discover in ensuing lessons, the violations of vowel harmony rules in roots are irrelevant to the discussion on suffixation. As such we won’t spend much time on these here.
Exceptions to vowel harmony can be categorized into four groups (Lewis 2000).
Because of diachronic change, some of the native words break fronting vowel harmony rules. However, don’t be surprise to hear the harmonic versions in some dialects especially in the countryside. Here are some examples from this category of words: elma ‘aple’ < alma elâ ‘hazel color’ < ala anne ‘mother’ < ana
In addition to the fronting vowel harmony violations, rounding harmony violations also occur with a few of the native words. However, these violations are generally predictable (labials cause the rounding of the following vowel, resulting in /u/): savun ‘defend’ kabuk ‘shell’
Compounds are formed by joining two or more words together (e.g. English word foot + ball). Here are some Turkish examples from this category of words: bugün ‘today’ < bu ‘this’ + gün ‘day’ Atatürk ‘last name given to the founder of Turkish Republic’ < ata ‘forefather’ + Türk ‘Turk’
Suffix -ken ‘while’ comes from the word iken with same meaning. This could explain why this suffix has only one variant
Vowel harmony rules are not observed with single variant suffixes. koşarken ‘while running’ gelirken ‘while coming’
As mentioned in the intro lessons, Turkish language has borrowed extensively from other languages. When words were borrowed into Turkish, the original phonemic integrity of the sources were largely maintained except for the phonemes that Turkish lacked. This process can also be observed in recent borrowings such as email, eposta and loder. kalemler ‘pens’ < kalem (Ar.) + -ler (PL) kitaplar ‘books’ < kitap (Ar.) + -lar (PL)
If you are interested in Turkish etymology, take a look at my sources for Turkish etymology in the reference section.