cause,reason,justification,ground这组同义词的一般含义是“原因”或“理由” cause用于表示具有明显因果关系的原因。reason有时能与cause换用，但上下文必须有能够查得出的或可以解释得出的因果关系。如果某“结果”是不言而喻的，也可以用reason表示“原因” Was the noise a cause of the illness,or were the complaints about noise merely a symptom? 噪音是病因呢，还是对噪音的抱怨仅仅是一种症状呢？ Every effect must have an adequate cause. 每一种结果都必须有充分的原因。 reason通常含有“理由”的意思 They are trying to find out the reason (or cause) of the terrible fire. 他们正在努力查寻那次可怕的火灾的原因。 The airport was built during the war,but for some reason it could not be used then. 这个飞机场是在大战期间建造的，但是由于某种原因当时没有能够使用。 The reason for this is that this plane is also a bicycle. 其原因是，这架飞机又是一辆自行车。 …，but I do not turn for protection to dreary cliches about respect for elders—as if mere age were a reason for respect.…… 但我不会为了维护自己而求助于尊重长辈之类的陈词滥调—似乎只要年老就是受到尊重的理由。 justification所表示的“理由”的内涵是“正当”或辩解 In the young there is a justification for this feeling. 在年轻人中有这种感觉是有理由的。 What' your justification for being late? 你迟到的理由是什么？ You have no justification for deserting your wife and children. 你没有理由抛妻弃子。 ground 所表示的“理由”包含着坚实的依据 On what ground do you suspect him? 你怀疑他的理由是什么？ The youngster has been excused by the law on the ground of his youth. 这个青年由于年轻而受到的赦免。