一、联合关系

联合关系的并列分句之间往往存在先后顺序，一般说来，次序不能颠倒。

and 同，和，于是，而且，然后

He helps me and I help him. 他帮我，我帮他。

When (=and just at this time 就在这时，然后 ),

He was wandering in the street when he suddenly caught sight of a traffic accident.

他正在街上闲逛，（这时）突然看到一场车祸。

I was just leaving when the telephone rang.

我正要离开，电话铃响了。

not only…but (also)…( 不仅……而且…… ),

Not only did he give us a lot of advice, but also helped us to study English.                                    

他不仅给我们出很多建议并且还帮助我学英语。

neither…nor… （既不……也不……）等。如：

Neither could theory do without practice, nor could practice do without theory.

理论没有实践不行, 实践没有理论也不行。

注： when 作这种用法时，主要用于下述几种情况表示“当某人或某物正在或正要做某事，就在这时突然又发生了另一事：

*… was/were doing sth., when sth./sb. did（瞬时动词）;

*… was/were about to do sth., when sth./sb. did;

*… was/were on the point of doing sth., when sth./sb. did 等句型中。

二、选择关系

常用的连词有 or (或者，否则), otherwise (否则), or else (否则), either...or (不是…就是) 。如：

Hurry up, or (else) you’ll be late.

快点，否则就会迟到了。

Will he still be there or will he have gone away?

你那时还在那里还是可能已经走了？

You must go early, otherwise you will miss the bus.

你好得早点走，否则就赶不上公共汽车了。

Either Tom is coming or his sisters are.

不是汤姆就是她的姐妹们要来。

三、转折关系

常用的连词有 but( 但是，可是，只是因为 ), while( 而、却 ), yet( 可是 ) 等。 如：

It never rains but it pours.

祸不单行。

I like tea while she likes coffee.

我喜欢喝茶而她喜欢喝咖啡。

She said she would be late, yet she arrived on time.

她说她会迟到，但她却准时到达了。

She looks very young, but she is already in her 30’s.

她看上去很年轻 , 可是她已三十多岁了。

此处，还有副 still (但是仍然）， however (然而)，neverthless (然而) 也表示转折关系。

He is good-natured; still I don''t like him.

他脾气很好 , 可是我还是不喜欢他。

The book is expensive; however, it''s worth it.

这本书很贵；却很值。

She was very tired, neverthelessshe kept on working.

她虽然很疲倦, 然而她却继续工作。

注意： but, while 不与 although 连用，但 yet, still 可与 although 连用。

Although she felt ill, she still went to work.

她虽然感觉不舒服，但她仍然去上班。

四、因果关系

常用的连词有 for （因为）和 so （所以，因此）等。如：

I am thirsty, for it is hot.

我口渴，因为天气太热。

The manager was ill so I went in her place.

经理病了所以我代她去。

注意： so 不与 because 连用