Because, As, Since or For

When do we use becauseassince and for?


Word Explanation Example
because The reason is very important in the sentence. The students could go home earlier because the teacher was ill.
Because the teacher was ill, the students could go home earlier.
as The reason is already known. As we read, we learn.
since The reason is already known. (more formal than as) Since we were in the computer lab, our English has improved.
for The reason is given at the end of the sentence.
The clause with for cannot be used in inital position.
We went to a small restaurant – for we were hungry.



We use because to give the reason of something that is important for the listener.

Because my brother didn’t keep his promise, I couldn’t go fishing.
Because I woke up late, we missed the bus.


When we want to emphasize the reason, we use the because clause at the end.

Why are you crying? I am crying because we lost the game.
We do not say as / since we lost the game.

I will punish you because you lie to me. (the reason is stressed)

As and Since

Like because, we use as and since to give reason but with as and since, the reason should already be known by the listener.

As we lost the final game, we couldn’t qualify for the semi-final.
(that we lost the final game is not something new to the listener.)

Since I was hungry, I wanted to eat something first.


For also introduces a new reason to the listener as because does. For-clause cannot be used in the beginning.

I had to stay at home and finish my assignment – for the deadline was soon.
I am going to Los Angeles for the NBA finals.


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