Form
because / as / since + Subject + Verb
(These are followed by a full sentence)
We cancelled the picnic because it was raining.
As I was very tired, I went to bed.
Meanings
Answering the question “Why?”
We use words like because, as, since, and due to to explain the cause of an event or situation.
Why was the flight cancelled?
→ Because of the storm.
Why did you go home early?
→ Because I felt ill.