3.but,yet,still,however,while(而,然而),when(那时)等连接并列句,常表示意义的转折及对比。
1)but表示转折、对比或对照(常与否定词连用)。例如:
Mary was a nice girl,but she had one shortcoming.
He scarcely knows a word of German,but he speaks French perfectly.
2)yet,still,on the contrary,on the other hand连接并列句,其连接力量不及but强,一般yet前可加and,其余的前可加but。例如:She got up early,(and)yet she failed to be there on time.She tried again and again,(but)still she didn't suc-ceed.I have nearly done it,but on the contrary,they have just begun.
3)however表示"然而"、"不可"、"可是"之意,和yet意思相近,可放在句首、句中、句尾。例如:
He said it was so,he was mistaken,however.
4)while表示对照关系。例如:
The strenghth of the collective is boundless(无限的),while that of the individual(个人的)is very limited.He asked his father why he couldn't hatch chickens while hens could.
5)when相当于and then,just then,at the time,一般放在第二个分句句首。例如:
We played outside till sunset when it began to rain.
She had not been married many weeks when that man's younger brother saw her and was struck by her beauty.
4.for,so,thus,therefore连接并列句表示因果关系。
1)for引导的分句表示附加或推断的理由、原因,常放在句尾,逗号隔开。例如:
Someone is coming,for the dog is barking.
Get down on your knees,for I'm going to kill you.
2)so,therefore,thus均表示"因此"的意思,但therefore更为正式。例如:
The Frenchman coughed day and night,so he decided to get some medicine for his cough.
My brother studied hard,thus he succeeded in passing the exam.
Mary didn't review her lessons,therefore,she couldn't answer the teacher's questions.
