Consonant mutation refers to changes that certain consonants undergo, typically when suffixes are added or in specific phonetic environments. This is primarily for ease of pronunciation.

1. Consonant Softening (Ünsüz Yumuşaması):

When a suffix starting with a vowel is added to a word ending in one of the voiceless consonants p, ç, t, k, these consonants often soften:

• p → b: Example: kitap + ı → kitabı (the book (accusative))
• ç → c: Example: ağaç + ı → ağacı (the tree (accusative))
• t → d: Example: kağıt + ı → kağıdı (the paper (accusative))
• k → ğ (usually) or g:
  • Example (k → ğ): çocuk + u → çocuğu (the child (accusative))
  • Example (k → g): renk + i → rengi (the color (accusative) - usually with 'nk')

2. Consonant Assimilation / Hardening (Ünsüz Benzeşmesi / Ünsüz Sertleşmesi):

If a word ends in one of the voiceless consonants (f, s, t, k, ç, ş, h, p - often remembered by the mnemonic 'FıSTıKÇı ŞaHaP'), and a suffix starting with 'c', 'd', or 'g' is added, these suffix consonants harden:

• c → ç
• d → t
• g → k

Example (d → t):

• kitap (ends in 'p' from FıSTıKÇı ŞaHaP) + -da (locative suffix starts with 'd') → kitapta (in the book), NOT kitapda.
• ağaç (ends in 'ç') + -dan (ablative suffix starts with 'd') → ağaçtan (from the tree), NOT ağaçdan.