1. 表示转折关系的并列连词。这类连词主要有 but, yet 等。如：
Someone borrowed my pen, but I don’t remember who. 有人借了我的钢笔，但我不记得是谁了。
He said he was our friend, yet he wouldn’t help us. 他说他是我们的朋友，但却不肯帮助我们。
2. 表示因果关系的并列连词。这类连词主要有 for, so 等。如：
The child had a bad cough, so his mother took him to the doctor. 这孩子咳得很利害，所以妈妈带他去看医生。
You are supposed to get rid of carelessness, for it often leads to serious errors. 你们一定要克服粗枝大叶，因为粗枝大叶常常引起严重的错误。
注意：for表示结果通常不能放句首，也不能单独使用。
3. 表示并列关系的并列连词。这类连词主要有 and , or , either…or , neither…nor , not only…but (also) , both…and , as well as 等。如：
He didn’t go and she didn’t go either. 他没去，她也没去。
The weather is mild today; it is neither hot nor cold. 今天天气很温暖，不冷也不热。
Both New York and London have traffic problems. 纽约和伦敦都存在交通问题。
It is important for you as well as for me. 这对你和对我都很重要。
People who are either under age or over age may not join the army. 年龄不到或者超龄的人都不得参军。