Questions & Answers about Otobüs büyük bir araç.
Why is the word order büyük bir araç instead of bir büyük araç?
Where is the word for "is" in this sentence?
In simple Turkish statements, the "to be" verb for "is" is often completely invisible! Just placing the subject (otobüs) and the description (büyük bir araç) next to each other is enough to mean "A bus is a big vehicle."
Why doesn't otobüs have bir in front of it to mean "A bus"?
When making a general statement about a whole category (like buses in general), Turkish uses the bare noun as the subject. Adding bir to the beginning here would make it sound like you are talking about one specific bus that happens to be big, rather than making a fact about buses in general.
Can I use araba instead of araç here?
No, because araba specifically means "car" (or cart/carriage). Araç is a broader category that means "vehicle" or "tool", which perfectly includes larger transportation like a bus.