Learn Turkish: Dün akşam bebek için süt ısıtıyor muydu? - Was she heating milk for the baby yesterday evening?

This tense combines the continuous suffix (-ıyor) with the past tense question word (muydu). First, we take the verb root ısıt- (to heat) and add -ıyor to make ısıtıyor (she is heating). Then, we add the question particle mu, a -y- buffer letter, and the past tense suffix -du. Together, ısıtıyor muydu means "was she heating?".

Where is the word for "she" in this sentence?

Turkish usually drops subject pronouns like o (he/she/it) because the verb ending already tells us who is doing the action. The word muydu doesn't have an extra personal suffix at the end (like the -m in muydum for "was I"), which tells us it's the 3rd person singular. Context determines whether it translates to he, she, or it.

Why is it just süt and not sütü?

Because the sentence is talking about heating "milk" in general, rather than a specific "the milk". In Turkish, direct objects only take the accusative case ending (which would make it sütü) if they are specific or definite.

Does the word bebek need any special ending before için?