This is the 592nd most frequent Arabic word.
السبب
The reason or the cause.
The word "السبب" is used here to indicate the cause or justification for an event or outcome.
السبب وراء نجاحه هو الاجتهاد.
The reason behind his success is diligence.
In this sentence, "السبب" is used to refer to an underlying cause or explanation for someone's action.
لا أعرف السبب الذي جعلك تتأخر.
I don't know the reason that made you late.
Here, "السبب" is a direct question asking for the explanation or cause of something.