1. however 副词，“然而”，可放于句首、句中或句末，总是用逗号与句子隔开。作连词时，表示“无论如何”，引导方式状语从句＝ no matter how…。

2. but 连词，“但是； 可是，然而； 而是”。 引导转折关系的两个并列句，可以置于句首，引导句子。

3. while并列连词，“而，然而”，连接并列句，表示前后句子意义上的对比和转折。

4. though作副词时也表示转折，语气比较弱，意为“不过，然而”，主要放于句末，用逗号与句子分开。

【活学活用】用though，but或however填空

1. She felt ill. She went to work，________，and tried to concentrate.

2. She looks very young，_____ she is already in her thirties.

3. I feel a bit tired. __________，I can hold on.

4. _________hot it is，he will not take off his coat.

5. I had a cold. It was not serious，_______.

【答案】

1. however 2. but 3. However 4. However 5. though