The Accusative case (Belirtme Hali) is used to mark the definite direct object of a verb. This means it specifies *which particular* person or thing is being directly affected by the verb's action. It answers the question "Whom?" or "What (specific one)?".

Suffixes:

The accusative suffix follows I-Type vowel harmony:

• If the last vowel of the noun is a or ı, add -ı.
• If the last vowel of the noun is e or i, add -i.
• If the last vowel of the noun is o or u, add -u.
• If the last vowel of the noun is ö or ü, add -ü.

If the noun ends in a vowel, the buffer consonant 'y' is inserted before the suffix.

Examples:

• Kitabı okudum. (I read the book.) (kitap + -ı)
• Elmayı yedim. (I ate the apple.) (elma + -yı)
• Kediyi gördüm. (I saw the cat.) (kedi + -yi)
• Okulu seviyorum. (I like the school.) (okul + -u)
• Gözlüğü buldum. (I found the glasses.) (gözlük + -ü, with k → ğ softening)

Definite vs. Indefinite:

It's crucial to distinguish between definite and indefinite direct objects.

• Definite (Accusative): Ben elmayı yedim. (I ate the apple. - a specific apple known to speaker/listener)
• Indefinite (Nominative): Ben elma yedim. (I ate an apple / some apple. - any apple)