它们是名词：
cause "原因、起因" result “结果” 互为反义词,因果关系
the cause of the fire 火灾的起因
the result of the fire 火灾的后果
reason “理由、原因”
Tell me the reason for your absence.告诉我你缺席的理由
You have reason to get angry.你有生气的理由.
That's the reason why he was late.那就是他迟到的原因.
它们三人又可以是及物动词.