İsim tamlaması — the noun-noun compound
When you put two nouns together in Turkish to mean 'X-of-Y' or 'X-kind-of-Y', the second noun takes a possessive suffix — usually -i (or -ı, -u, -ü by vowel harmony, or -si after a vowel). 'Turkish coffee' is Türk kahvesi — literally 'Turk its-coffee'. 'Workplace' is iş yeri — 'work its-place'. The first noun stays bare; the suffix on the second is what tells you the two belong together.
Why the second noun takes -i
Turkish marks the relationship on the head of the phrase, not the modifier. In English we say 'student book' — two bare nouns. In Turkish you have to glue them: öğrenci kitabı. The bare form öğrenci kitap would just be two unrelated words. The -ı at the end says 'this book belongs to the category of student'. Same idea: diş fırçası (toothbrush — 'tooth its-brush'), el çantası (handbag — 'hand its-bag'), göz doktoru (eye doctor — 'eye its-doctor').
The four-way harmony of -i
Pick the suffix vowel by harmony with the last vowel of the second noun. After a, ı → -ı: Türk kahvesi? No — let's check: kahve ends in e, so → -si. After e, i → -i: iş yeri ('work its-place'), ev sahibi ('house its-owner' = host). After o, u → -u: göz doktoru, okul müdürü. After ö, ü → -ü: göz doktoru uses -u, but şehir müzesi uses -si because müze ends in e. When the second noun ends in a vowel, you insert a -s- as a buffer: kahve → kahvesi, araba → arabası, müze → müzesi.
First-noun + second-noun, never the other way
The descriptor comes first, the head second. Türk kahvesi = 'Turkish coffee' (a kind of coffee). kahve Türkü would be nonsense. Same for çay bardağı ('tea its-glass' = a tea glass), deniz kenarı ('sea its-side' = seaside), iş arkadaşı ('work its-friend' = colleague). The first noun is like an adjective; the second carries the relationship suffix.
Compound vs. possessive
Compare two structures. Türk kahvesi ('Turkish coffee', a kind) — first noun bare, second with -i. Türkün kahvesi ('the Turk's coffee', a specific person's) — first noun with genitive -in, second with -i. The genitive on the first noun is what makes it a real possessive. Without it, you have a compound — a name for a thing. The compound is the everyday workhorse: shops, dishes, body parts, places.
Stacking compounds
You can chain them. çocuk doktoru = 'child its-doctor' = pediatrician. çocuk doktoru randevusu = 'pediatrician its-appointment'. The suffix lands on the very last noun in the chain. Newspapers love these: devlet hastanesi başhekimi ('state hospital its-chief-physician'). Don't be intimidated — once you can spot the bare-bare-suffix pattern, long compounds parse easily.
