Learn Turkish: Bakıcı bebeği saat kaçta uyuttu? - At what time did the nanny put the baby to sleep?

The root is uyu- (sleep). Because this root ends in a vowel, we add the causative suffix -t to make uyut-, which means "to cause to sleep" or "to put to sleep". Finally, we add the past tense suffix to get uyuttu.

Why does uyuttu take the past tense suffix -tu instead of -du?

This is due to consonant assimilation. The causative verb stem uyut- ends in the voiceless consonant t. When a suffix starting with d (like the past tense -du) attaches to a voiceless consonant, the d hardens into a t to match it, giving us -tu.

Why is the word for baby written as bebeği instead of just bebek?

Two rules apply here. First, bebek takes the accusative (specific direct object) suffix -i because the baby is the specific target being put to sleep. Second, when a suffix starting with a vowel is added to a word ending in k, the k softens into a ğ (soft g), resulting in bebeği.

Why do we say saat kaçta instead of just saat kaç?