Learn Turkish: Karnım tok, teşekkürler.

The Turkish word for stomach or belly is karın. When a suffix starting with a vowel is added, like the 'my' suffix -ım, the second vowel in the root word drops out. This makes karın + -ım become karnım. This vowel dropping is very common with body parts in Turkish.

Why does the Turkish sentence literally say 'My belly is full' instead of 'I am full'?

While you can technically say Tokum (I am full), saying Karnım tok (My belly is full) is a set phrase. It is the most standard, natural way to decline food and tell someone you are no longer hungry in Turkish.

Can I use tok to describe a full glass of water?

No, tok specifically means 'full' in the sense of a person or animal having eaten enough food. It is the direct opposite of aç (hungry). To say a physical object or space is full, you must use the word dolu.