Learn Turkish: Kışla çok büyük mü? - Is the barracks very big?

It looks like it could be kış (winter) plus the -la (with) ending! Historically, a kışla was a place where soldiers stayed during the winter. But today, it is a single, stand-alone noun meaning "barracks" or "military base".

English uses "barracks" which looks plural. Why isn't it kışlalar in Turkish?

In English, "barracks" is a tricky word that ends in "s" even when we mean just one complex. Turkish is more straightforward: kışla is singular (one barracks). If you meant multiple different military bases, you would use the plural kışlalar.

Why do we use mü instead of mi for the question particle?

The question particle always follows 4-way vowel harmony based on the last vowel of the word right before it. Since the last vowel in büyük is ü, the question particle changes to match it, becoming mü.

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

In Turkish, simple present tense sentences don't use a separate "is" or "are" verb. By placing the subject (kışla), the description (çok büyük), and the question particle (mü) together, the "is" is naturally built into the meaning.