n (1)原因，理由(fact or cause that explains why sth exists or occurs)[C，U][N(for)，N+to-inf，N+that，N+wh]：～(s) for sb's action/sb's being late/sb's not going/what sb does 某人行动/迟到/不去/所做之事的原因;He has sufficient/adequate/good～for doing so. 他有足够/充足/很多的理由那样做。You don't have any/do have many～s to leave me. 你没有任何理由/确实有充分的理由离开我。There is no～to fear him. 没有任何理由害怕他。The～that/why I am late is that my car broke down. 我迟到的原因是我的车坏了。for no/some/the/the simple～无缘无故/因某种原因/因这个原因/因简单的原因;for one/some～or other 由于某种原因;for～s of space/health/tactics/convenience 出于空间/健康/策略/方便的缘故;He complained with～that nobody told him the truth of fact. 他抱怨没有人告诉他事实真相，这不无道理。〖同〗ground，cause;

(2)理智(性)，思维(推理)能力(ability to think，understand，and make decisions，clearly and sensibly;mental balance)[U]：lose one's～丧失理智(发疯);be restored to～恢复理智(正常状态);use～动脑子想想;Man has～. 人类有理性。〖同〗rationality，brains;〖反〗unsoundness;

(3)道理 (statement or fact that justifies or establishes the truth of a conclusion，statement)[U]：listen to/hear/see～服从/服从/明白道理;be open to～服理;There is～in what you say. 你说的有道理。

beyond/past all reason 不讲(没有)道理：What he asked for is (goes) beyond/past all～. 他所要求的完全没有道理。

by reason of 因为，由于(infml)：The arrangement was cancelled by～of his illness. 因为他病了，原来的安排被取消了。

for reasons/some reason best known to oneself 自有某人的道理(尤joc)：For～s best known to herself，she has decided to sell the car. 她决定把车卖掉，这自有她的道理。

in/within reason 合情合理的：I'll answer anything you ask within/in～. 我会回答你提出的任何合理的问题。

stand to reason 理所当然，自然，站得住，合乎道理：What you say stands to～. 你说得有道理。If you have a driver's license，it stands to～you can drive. 如果你有驾驶执照，你理所当然可以开车。

v (1)思考，分析，推理 (use the ability to think clearly and sensibly)[I]：Do you think some animals can～? 你认为有些动物会思考吗? man's ability to～人的思考能力;～soundly/very clearly分析得合理/非常清楚;

(2)推论，(说出)道理(think logically or draw(logical conclusions)from facts)[T+that，无pass]：He～ed that she was guilty as charged. 他推断，正如被指控的那样，她有罪。She～ed that since she posted the letter a week ago，her mother should receive it now. 她推断说，既然她一个星期前就把信寄出去了，她母亲现在该收到了。

reason sb into/out of 通过讲道理说服某人去做/不去做：Let me try to～him into joining us. 我来试试看能否说服他加入到我们的行列来。I have～ed her out of her wish to go to America. 我已经说服她放弃了去美国的想法。

reason out (v adv)(通过分析)解决(vt)：He～ed the problem out and came to a conclusion. 他分析了那个问题之后得出了结论。

reason with (v prep)和……讲道理(vt)：I meant to～with you，but you won't～. 我要和你讲道理，可是你却不讲理。

→′reasoned adj 合情理的;′reasoning n 推理，分析;′reasonable adj;

【用法】reason作名词时不要用 “the reason is because...”，因为 “the reason is...”与because 是同一个意思。 应该用that替代because，如：The reason he is absent is that he is ill. (他没来的原因是因为他病了。) 或：He is absent because he is ill. (他没来，因为他病了。)

【辨异】reason与cause、ground和motive的区别见CAUSE。