Learn Turkish: Onlara buğday vermezsin. - You do not give them wheat.

The verb root is ver- (give). To say "you do not give" in the simple present (aorist) tense, we add the negative suffix -mez and the personal ending -sin (for "you"). Because ver- has a front vowel (e), we use -mez instead of -maz.

Why use vermezsin here instead of vermiyorsun?

Vermiyorsun is the present continuous ("you are not giving" right now). Vermezsin uses the aorist tense, which talks about habits, general truths, or typical behavior. It means "as a rule, you do not give."

Why is it onlara instead of just onlar?

The verb vermek (to give) needs a target—who are you giving it to? In Turkish, we show this direction using the dative case ending. Onlar (they) becomes onlara (to them).

Why doesn't buğday have an accusative ending like buğdayı?

Because "wheat" is a general, unspecific object here. You are not talking about a specific batch of wheat ("the wheat"), just wheat in general. When a direct object is non-specific, it doesn't take an ending and usually sits right before the verb.