reason n. 原因;理由
(1) + to do sth. You haven't any reason to leave me.
(2) + for sth. / doing People must have a reason for saying such things.
(3) + 从句;从句用why / for which引导 That is the reason why you should leave.
(4) for + reason，为了某种原因He is retiring for reasons of health.
the cause of the fire 火灾的起因(引起某种后果的起因)
the reason for being late 迟到的理由(做某件事的理由)