Vowel harmony decides which vowel a suffix uses, but it is only half of Turkish morphophonology. The other half is about consonants: stems and suffixes trade their consonants back and forth depending on what they bump up against. These mutations are why kitap ("book") becomes kitabı, why renk ("colour") becomes rengi, and why the locative is evde but kitapta. Together with vowel harmony, they fully determine a suffix's spelling — so once you hold both halves in your head, you can write any inflected word correctly without guessing. This page is the map; each row points to a page that does the detail.
The three forces at a glance
There are three distinct things going on, and it helps enormously to keep them apart. Two of them are about voicing at the boundary between stem and suffix, working in opposite directions; the third is about what happens at the end of a word in isolation.
| Mutation | Where it happens | Direction | Example |
|---|---|---|---|
| Stem-final softening | end of stem, before a vowel suffix | voiceless → voiced | kitap → kitabı |
| Suffix-initial hardening | start of suffix, after a voiceless stem | voiced → voiceless | -DA → kitapta |
| Final devoicing | end of word, in isolation | voiced → voiceless | kitab- → kitap |
The unifying idea is assimilation by voicing: at the seam between two pieces of a word, a consonant tends to agree in voicing with its neighbour. Softening and hardening are the same principle pointed in two directions. Final devoicing is a separate "tidy-up" rule that affects the very end of a word.
1. Stem-final stops soften before a vowel suffix
A word ending in a voiceless stop — p, ç, t, k — frequently softens it to the matching voiced consonant — b, c, d, ğ/g — when a suffix beginning with a vowel is attached. The voiced consonant is "trapped" between two vowels and the language smooths the transition.
Kitabı bir günde bitirdim, çok sürükleyiciydi.
I finished the book in a day; it was a real page-turner.
Bahçedeki ağacı fırtına devirmiş.
The storm has knocked over the tree in the garden.
Kitap → kitabı (p → b) and ağaç → ağacı (ç → c). The t → d case (kanat → kanadı) and the k → ğ/g case (renk → rengi) get their own treatment because each has its own quirks. This softening is genuinely common but not automatic — many words keep their voiceless consonant — so it is worth its own deep dive on the p → b, ç → c, t → d page, with the k alternation on the k → ğ / g page.
Köşedeki renk seçeneklerinden hangisi sana daha çok yakıştı?
Of the colour options on the corner, which one suited you better?
Renk → rengi when suffixed: after n, the k softens to g (not ğ) — one of the small sub-rules the k page handles.
2. Suffix-initial consonants harden after a voiceless stem
Now the mirror image. Some suffixes begin with a consonant written in the guide as a capital archiphoneme — the D of the locative -DA and past -DI, the C of the agent -CI. After a voiceless stem-final consonant (p, ç, t, k, s, ş, h, f), that D hardens to t and that C hardens to ç.
Akşama kadar kütüphanede ders çalıştım.
I studied at the library until evening.
Defteri çantamda unuttum, derste not alamadım.
I left my notebook in my bag and couldn't take notes in class.
Kütüphane-de (voiced stem → -de) versus ders-te (voiceless s → -te): same suffix -DA, hardened on the right-hand example. And the agent suffix:
Köşedeki simitçiden iki simit aldım.
I bought two simit from the simit-seller on the corner.
Simit-çi ("simit-seller"): the -CI suffix hardens to çi after the voiceless t. Compare bal-cı ("honey-seller"), where the voiced l keeps it -cı. The full hardening rule, with the complete voiceless set, lives on the D and C hardening page.
3. Final consonants devoice in isolation
The reason a softening stem looks like it "changes a letter" is the third rule: Turkish does not allow a voiced stop at the very end of a word, so the underlying voiced consonant devoices in the bare citation form. The dictionary form kitap is the devoiced version of an underlyingly voiced stem; suffixation simply removes the word-final position and lets the true b resurface.
Bu kitap çok meşhur ama henüz okumadım.
This book is very famous, but I haven't read it yet.
Sınava çalışmak için gidiyorum, akşam görüşürüz.
I'm off to study for the exam; see you this evening.
Kitap in isolation (devoiced) vs kitabı suffixed (voiced). The verb git- ("go") shows the same thing inside a conjugation: gitmek in the infinitive but gidiyor ("is going") once a vowel follows. Because the citation form hides the real stem, it is good practice to learn a noun together with a vowel-suffixed form — kitap, kitabı — so you know whether it softens. This is the subject of the final-devoicing page.
How the two halves combine
Vowel harmony and consonant mutation operate together on every suffix, and they are independent — you resolve each separately and the answers do not interfere. Take the locative -DA on three stems:
Çocukken yazları köyde dedemlerde kalırdık.
As a child, in summers we'd stay at my grandfather's in the village.
Köy-de: voiced stem, so D → d; front vowel ö, so A → e. Kitap-ta: voiceless p, so D → t; back a, so A → a. Ders-te: voiceless s, so D → t; front e, so A → e. The consonant choice and the vowel choice are made by two different rules and then simply written together. That independence is what makes the system learnable: you are never juggling one giant rule, only two small ones.
Common mistakes
❌ Kitapı masaya koydum.
Incorrect — keeping voiceless p before a vowel suffix.
✅ Kitabı masaya koydum.
I put the book on the table.
A vowel suffix softens the stem-final p to b: kitabı, not kitapı.
❌ Otobüsde bekliyorum.
Incorrect — not hardening D after the voiceless s.
✅ Otobüste bekliyorum.
I'm waiting on the bus.
After voiceless s, the locative -DA hardens to -te.
❌ Rengin adı neydi?
Incorrect spelling intent — note rengi, not renki, when softened.
✅ Bu rengi çok beğendim.
I really like this colour.
After n, the final k of renk softens to g: rengi, not renki.
❌ Simitcide buluşalım.
Incorrect — not hardening C after the voiceless t.
✅ Simitçide buluşalım.
Let's meet at the simit-seller's.
The agent -CI hardens to çi after voiceless t: simitçi.
Key takeaways
- Three forces complete the suffix system: stem-final softening, suffix-initial hardening, and final devoicing.
- Softening (voiceless → voiced before a vowel) and hardening (voiced → voiceless after a voiceless stem) are the same voicing assimilation in opposite directions.
- Final devoicing is why citation forms hide the true stem (kitap vs kitabı); learn nouns in pairs.
- Consonant mutation and vowel harmony are independent — resolve each separately, then write both.
- Follow the links for the detail: softening p/ç/t, k → ğ/g, D/C hardening, final devoicing.
Now practice Turkish
Reading grammar gets you part of the way. The exercises are where it sticks — free, no signup needed.
Start learning Turkish→Related Topics
- Softening: p→b, ç→c, t→dA2 — The stem-final softening of p, ç and t to b, c and d before a vowel suffix — why it happens, the written result, and the large set of monosyllables and loans that do not soften.
- Softening: k→ğ and k→gA2 — The most frequent stem-final softening — k turns into ğ before a vowel suffix in most polysyllabic words (ayak→ayağı), but into g after n (renk→rengi), while many monosyllables and loans keep their k.
- Suffix Hardening: the D and C ArchiphonemesA2 — The mirror image of softening — a suffix-initial D hardens to t and a suffix-initial C hardens to ç after a voiceless stem, so the locative is kitapta (not *kitapde) and the past is gitti (not *gitdi).
- Final Devoicing in Citation FormsB1 — Why Turkish dictionary forms end in voiceless stops even when the stem is really voiced — kitap hides kitab-, git- hides gid- — and why you should learn every such word together with a vowel-suffixed form.