[注意]下列情况只能用whether不能用if：①引导主语从句,②引导表语从句,③引导从句作介词宾语,④引导不定式短语,⑤引导让步状语从句,⑥在动词discuss之后,⑦在wonder / not sure之后,⑧在if与whether含义易混时。如：Whether it is a fine day next Sunday is still a question.(下个星期天是不是个好天还是个问题)(引导主语从句) / Please ask him whether to go there with a raincoat or not.(请问一下带不带雨衣去那儿)(作动词的宾语) / Hainan is the place to be, whether it’s summer or winter.(海南是个该去的地方无论冬夏)(引导让步状语从句)/ Please let me know whether you need my help.(请告诉我你是否需要我的帮助)(引导宾语从句)(如果换成if则还可能表示“如果你需要我的帮助请告知”)

　　(3)while、when、as的用法区别：while常表示一个较长的动作,它引导的从句动作与主句的动作是只能是同时发生的、是平行的;when可以表示较短的动作也可以表示较长的动作,主句和从句的动作可以同时发生也可以先后发生;as与上两词同义,可替换while和when, 表示主句和从句的动作同时发生,常译为“一边……一边……”。如：Please do not trouble me while I am writing my homework.(我写作业时请不要打扰我)/ I’ll go home when I have finished my job.(我干完了活儿就回去)(不是同时发生)/ They were running quickly across the road when they heard the sound of a truck coming.(他们正快速地穿过马路忽然听到了卡车开来的声音)/ As we walked in the dark street, we sang songs and talked loudly.(当我们在黑洞洞的街上走路时我们高声地唱歌说话)

　　(4)till/until与not…till/until的区别：前者表示一个延续性的动作,后者表示一个才开始的动作。如：I will stay here and watch the baby until you return.(我会呆在这里看着娃娃直到你回来)(stay这个动作一直进行到你return) / They won’t go on working until they get what they think is reasonable.(他们要到获得了他们认为合理的东西时才会继续干下去的)

　　另外till与until基本可以互换,但是在句首时只能用until,不能用till. 如：Until the last minute of the match we kept playing.(我们坚持到比赛的最后一分钟)/ Not until he had finished his work did he go home.(直到做完工作他才回家)(倒装句)

　　(5)though与although的区别：两个词都表示“虽然”,均不可以与but同时使用,但在句中可加still或yet连用。although“尽管、虽然”仅作连词,比较正式,一般可以换为though; though“虽然、尽管、即使”,①还可以与even连用(=even if),表示“即使、纵然”,②作副词时意思是“然而、不过”,不能放在句首。③although不能放在句末，though则可以，用“，”隔开。如：He passed the exams although illness prevented him from going to classes.(尽管疾病使他无法上课但是他还是通过了考试)/ she won’t leave the TV set,even though her husband is waiting for her for the supper.(她不愿离开电视机虽然丈夫在等她吃饭)/ It was a quiet party. I had a good time, though.(这是个不热闹的聚会尽管如此我还是玩得很开心)

　　(6)prefer to…rather than…与prefer…to…的区别：prefer to…rather than…后面都是用动词原形,prefer…to…都是用动名词或名词。如：I prefer English to Japanese.(与日语相比我更喜欢英语)/ I prefer to learn English rather than learn Japanese. (与日语相比我更喜欢学英语)

　　初一连词联系：

　　1.I had to go to work by taxi_______ I got up late this morning.

　　A. so B. but C. and D. because

　　用and, but, so填空：

　　Jane didn’t work hard last term, _______ she failed many subjects.

　　I like playing badminton, _______ my sister doesn’t.

　　David got up early this morning, _______ he got to school on time.

　　Lucy bought a book on animals, _______ she liked it very much.