These are all words for a cause or an explanation for sth that has happened or that sb has done.以上各词均指事情发生或做某事的原因、理由、解释。
reason a cause or an explanation for sth that has happened or that sb has done; a fact that makes it right or fair to do sth指某事发生或做某事的原因、理由、解释、道理：◆He said no but he didn't give a reason.他说不行，但没有说明原因。
explanation a statement, fact or situation that tells you why sth has happened; a reason given for sth指解释、说明、阐述：◆The most likely explanation is that his plane was delayed.最可能的解释是他的飞机晚点了。◆She left the room abruptly without explanation.她未作解释就突然离开了房间。
grounds(ratherformal) a good or true reason for saying, doing or believing sth指说、做或相信某事的充分理由、根据：◆You have no grounds for complaint.你没有理由抱怨。
basis(ratherformal) the reason why people take a particular action指原因、缘由：◆On what basis will this decision be made?将基于何种原因作出这一决定呢？
excuse a reason, either true or invented, that you give to explain or defend your behaviour; a good reason that you give for doing sth that you want to do for other reasons指为自己行为所作的辩护、借口、理由：◆Late again! What's your excuse this time?又迟到了！你这次有什么借口？◆It gave me an excuse to take the car.这使我有理由开车去了。
motive a reason that explains sb's behaviour指动机、原因：◆There seemed to be no motive for the murder.这起谋杀案看不出有什么动机。
justification(ratherformal) a good reason why sth exists or is done指事物存在或做某事的正当理由：◆I can see no possible justification for any further tax increases.我看不出还能提出什么理由来加税了。
grounds or justification?用 grounds 还是 justification？
Justification is used to talk about finding or understanding reasons for actions, or trying to explain why it is a good idea to do sth. It is often used with words like little, no, some, every, without, and not any. Grounds is used more for talking about reasons that already exist, or that have already been decided, for example by law: moral/economic grounds. * justification 用来表示找出或明白做事的理由，或解释要做的事，常与 little、no、some、every、without 和 not any 等词连用。grounds 多指已存在的原因或已决定的（如法律上的）根据：moral/economic grounds（道德/经济原因）。
pretext(ratherformal) a false reason that you give for doing sth, usually sth bad, in order to hide the real reason指为掩盖做某事（通常为不好的事）的真正理由而找的借口、托辞：◆He left the party early on the pretext of having to work.他借口有事要处理，早早离开了聚会。
Patterns
(a/an) reason/explanation/grounds/basis/excuse/motive/justification/pretext for sth
🔑[sing.]thewaythingsareorganizedorarranged基准；准则；方式◆onaregular/permanent/part-time/temporarybasis以定期/永久/兼职/临时性的方式◆onadaily/day-to-day/weeklybasis按每天/每周一次的标准🔑[C, usually sing., U]theimportantfacts, ideasoreventsthatsupportsthandthatitcandevelopfrom基础；要素；基点◆Thebasisofagoodmarriageistrust. 美满婚姻的基础是信赖。◆Thisarticlewillformthebasisforourdiscussion. 这篇文章将作为我们讨论的基点。◆Thetheoryseemstohavenobasisinfact. 这一理论似乎没有事实根据。basisfoundation ⬥ base
These are all words for the ideas or facts that sth is based on.以上各词均指基础、根据。
basis[usually sing.] a principle, an idea or a fact that supports sth and that it can develop from指基础、要素、基点：◆This article will form the basis for our discussion.这篇文章将作为我们讨论的基点。
foundation[C, U] a principle, an idea or a fact that supports sth and that it develops from指基本原理、基础、根据：◆Respect and friendship provide a solid foundation for marriage.尊重和友爱是婚姻的牢固基础。◆The rumour is totally without foundation(= is not based on any facts).这谣传毫无事实根据。
basis or foundation?用 basis 还是 foundation？
Foundation is often used to talk about larger or more important things than basis.与 basis 相比，foundation 常用以指更大、更重要的事物：◆He laid the foundations of Japan's modern economy.他奠定了日本现代经济的基础。◆These figures formed the basis of their pay claim.这些数字是他们要求提高工资的根据。
base[usually sing.] an idea, a fact or a situation from which sth is developed指根据、出发点：◆His arguments have a sound economic base.他的论点在经济上有充分的根据。
Patterns
a/the basis/foundation/base for/of sth
a secure/solid/sound/strong/weak basis/foundation/base