可是的英文：
but
however

参考例句：

Be a pal and..
有点事相求，可是..。

This is your big bread.
这可是你的大好机会。

What you said is a promise which is as good as a thousand bars of gold.
你的话可是一诺千金。

Don't give me any ifs and buts.
别再跟我说“如果”、“可是”了。

To use a sporting phrase, I had not been once “at fault”.
套句体育界的行话，我可是“百发百中”。

The dew fell, but with propitious softness.
露水降落，可是带着慈祥的温柔。

I asked him where to go, but he didn't reply.
我问他去哪儿，可是他不回答。

You should have seen the teacher wig out!
你可是没看到老师发脾气的样子！

But some states run counter to the national trend and experienced a drop in the population of preschool children.
可是有些州与全国趋势背道而驰。学龄前儿童人数下降。

The job doesn' t sound very exciting but I' ll give it a whirl.
这个工作听起来没什么意思，可是我还是要去试一试.。

however是什么意思：
conj. 然而，可是，不过
adv. 无论如何，不管怎样；究竟怎样，到底如何

However did you know that?
你到底怎么知道那件事的？

This, however, upset and displeased the peasants.
但这都使农民很不高兴。

However, their intentions are honourable.
然而，他们的初衷是高尚的。

The equations generated, however, are not linear.
但所形成的方程不是线性的。

However, the screens have a limited lifespan.
不过，这种荧屏的使用寿命有限。