26 as long as; in case; in case of; in the case of; in the event of; in the event that; on condition of; on condition that; on the understanding that; provided that; providing that; so long as
● 本组词组一般意为“如果”“只要”，除in case of和in the event of, in the case of, on condition of为复合介词词组外，其余均为起连词作用的词组，引导状语从句。
● as long as和so long as可互换，只是后者更为强调。如：As long as you have made up your mind any way, I’ll but have to respect your choice.（既然你已下定决心，我只得尊重你的选择。）So long as I can, I must do it.（只要我能做到，我就做。）He may use my room as long as he cleans it up afterwards.（如果他事后能打扫干净，就可以用我的房间。）You may borrow the book as long as you keep it clean. （你可以借这本书，只要你别把它弄脏。）I will go as long as my expenses are paid. （如果有人替我付我的费用，我就去。）You’re welcome to stay with us so long as you share the rent. （欢迎你同我们住在一起，只要你分担房租。）You can go out this evening so long as you promise to be home by midnight. （如果你答应在半夜以前回到家里，今晚你就可以出去。）So long as electric current flows through a wire, there is a potential difference. （只要有电流通过，导线就有电位差。）
● in case是连词，in case of是介词，前者引导条件从句，后者接名词、ing分词等作宾语，如：In case anybody telephones me, tell him I’ll be back at seven.（如果有人打电话给我，告诉他，我七点钟回来。）Take your raincoat in case it rains.（带上雨衣，以防下雨。）The night watchman is in the office in case there is a fire.（值夜班的人留在办公室，为了防止火灾。）I was advised to arrange for insurance in case I needed medical treatment while I was abroad on vacation.（如果我去国外度假需要治病，他们建议我去办医疗保险。）Peter took up the rear, armed with a large hammer in case of emergencies.（彼得殿后，他手拿一把大锤，以防出现紧急情况。）In case of fire, ring the alarm bell.（万一失火的话，请按警铃。）In case of rain, the match will be put off.（万一下雨，比赛就延期。）You may refer to your dictionary in case of difficulty.（万一碰到困难，你可以查词典。）
● in the case of意为“对于”“至于”“就……来说”，后接名词、代词、ing分词作宾语。如：They have to retreat in the case of the present circumstance.（就目前情况来说，他们必须退却。）Poverty depresses most people, in the case of my father it was otherwise.（贫困使多数人消沉，但我父亲却并不这样。）In the case of your broken leg, the surgeon could hardly do anything.（关于你那条摔坏的腿，外科医生无能为力。）In the case of a physical change no new substance is formed.（就物理变化而言，没有新的物质产生。）
● in the event of后接名词或ing分词，in the event that引出状语从句，美国英语中有时that可省略，意为“如果”等。如：In the event of rain the sports meeting would be postponed until next month.（万一下雨，运动会推迟到下月举行。）In the event of his death, his son will take over the farm.（万一他死了，他儿子将接管农场。）He won’t be able to preside over the closing ceremony in the event of being sick.（万一他病了，就不能去主持闭幕式。）She will be dismissed in the event of her doing such a thing again.（如果她下次再做这样的事，她将被开除。）In the event that the roads are icy, we shall not come.（如果道路结冰，我们就不来了。）Those who play with fire will get burned in the event.（玩火者，终必自焚。）We were afraid he would be serious on stage, but in the event he performed beautifully.（我们担心他在台上会一本正经的，可是结果他演得精彩极了。）In the event （that） our team wins, there will be a big celebration.（如果我队赢了，将大大庆祝一番。）
● on condition of后接名词、名词词组等，on condition that后接从句，两者意思相同，可以互换，只不过句子要作调整。on condition that比较常用一些。如：He’ll accept your invitation to the party on condition that you are sincere.（如果你真诚地邀请他来参加聚会，他会接受的。）I’ll come on condition that my sister is invited too.（如果也邀请我妹妹，我就来。）We’ll accept the paper on condition that you allow us to make some alterations. （如果你允许我们作些改动的话，我们就可以接受这篇论文。）On condition of your signing this receipt I will pay you the money. （如果你在收条上签字，我就付你钱。）
● on the understanding that同on condition that,只是它较正式。如：I shall consent to your proposal on the understanding that you bear the expenses.（我可以同意你的建议，但以你负担费用为条件。）They divorced on the understanding that the husband could see the children every weekend.（他们以丈夫可于每周末看望孩子们为条件离婚了。）I accepted the offer on the understanding that I need not keep regular office hours.（若不要求我坐班，我就接受这份工作。）He will take the house only on the understanding that it is repaired.（如果这所房子修好了，他就要。）
● provided that与providing that一般可互换，不过前者是正式用语，后者为一般用语。前者引导的从句多放在主句之后，而后者引导的从句多在主句前，有时用于口语或商业用语，少用。如：You can go out to play provided that you finish your homework first.（如果你先完成作业，你就可以出去玩。）Provided that you pay me back by Saturday, I’ll lend you the money.（如果你在星期六之前把钱还给我，我就把钱借给你。）I’ll go, provided that you go too.（只要你去，我才会去。）They are prepared to be generous, provided that it is not their own money they are spending.（只要花的不是他们自己的钱，他们才会出手大方。）He should be home soon providing [provided] that the buses haven’t been held up.（只要公共汽车没误点，他应该就到家了。）During lucid intervals he may enter into a legal contract, a martiage, etc. providing that at the time he is capable of entering into such matters. （在清醒的间隙，病人可以订立法律性的契约，如婚约等，如果他当时能办这类事的话。）