but 与 however的用法区别

两者均可表示转折或对比，意为“但是”、“可是”、“然而”等，但有区别：

1. 表示转折时，but 是连词。如：

He is young but very experienced. 他虽年轻，但经验很丰富。

He has three daughters but no sons. 他有3 个女儿，但没有儿子。

He likes sports, but his wife likes music. 他喜欢运动，而他妻子则喜欢音乐。

2. however 表示“然而”、“可是”时，有的词书认为它是连词，有的词书认为它是副词。之所以将其视为副词，也许是因为像许多副词一样不仅能位于句首，而且能位于句中(注意前后使用逗号)，甚至句末 (注意其前也用逗号)。如：

Later, however, he changed his mind. 可是他后来改变了主意。

He hasn't arrived. He may, however, come later. 他还没有到，不过他等会儿可能会来。

He said that it was so; he was mistaken, however. 他说情况如此，可是他错了。

注：以上各例中的 however 不能换成 but，但可用 but 来改写。如：

He said that it was so, but he was mistaken. 他说情况如此，可他错了。

3. 当连接两个句子时，其前通常应用分号，或另起新句。如：

It's raining hard; however, I think we should go out. / It's raining hard. However, I think we should go out. 雨下得很大，但我想我们还得出去。

注：上例中的 however 不能换成 but，但可用 but 来改写 (注意所用标点的变化)。如：

It's raining hard, but I think we should go out.