一、都可以表示转折

I like sports but I don't like swimming.

我喜欢运动，但我不喜欢游泳。

She is young but very experienced.

她虽然很年轻，但很有经验。

换成however：

I like sports，however，I don't like swimming.

我喜欢运动，但我不喜欢游泳。

She is young, however，she's very experienced.

她虽然很年轻，但很有经验。

二、都可以表示对比

She is beautiful，but not as smart as you are.

她是漂亮，但她没你聪明啊。

She is beautiful，however，she's not as smart as you are.

她是漂亮，但她没你聪明啊。

不同点：

1、连接两个句子时，but可以直接带句子，however后面需要用逗号“，”与句子隔开，见上述例子。

2、“but”可以连接句子和词、短语；“however”一般只跟句子。

He looks small but healthy.

他看起来个子虽小但很健康。

but可以连接两个词，但是改成用however的话，就只能用句子。

He looks small，however，he's very healthy.

他看起来个子虽小但很健康。

3、“however”的位置比“but”灵活。

He hasn't arrived yet. However，he will come soon.

He hasn't arrived yet. He will, however, come soon.

He hasn't arrived yet. He will come soon, however.

他现在还没到，但是他很快就会到了。

however可以放在句子的句首、中间，或最后。

He looks small but healthy.

He looks small，but he's healthy.

他看起来个子虽小，但很健康。

but一般只放在它连接的句子的句首；或者在连接两个并列词组时，房子中间。

4、“however”可以表示惊奇或强调，“but”不能。

However did you get here without a car? 

没有汽车你究竟是怎样来的呢?

5、“however”可以引导让步状语从句，“but”不能。

However it may be, I shall take your word. 

无论如何，我将会相信你的话。

However what you do, I won't forgive you.

无论你做什么，我都不会原谅你。