but,though,however 有什么区别

ut 是连词,连接两个并列句,中间用逗号隔开.表示转折
如： I wanted to buy a book, but I don't have enough money.
though 是副词,但在句中的成分相当于连词.引导从句,不能与but 连用,可以放句首或者句中.意思是尽管
如：Though it is so hot I have to go outside.
I have to go outside though it is so hot.
however 也是副词,剧中成分相当于连词.可以放在句首或句中,后面一定要用逗号.表转折.放句首时,与前面的句子是转折的连接.放句首时,前后用逗号隔开
如：I wanted to buy a book, however, i do not have enough money.

but:但是,语气要比however 强
however:可是,然而.语气较弱,通常位于句中.
"I'd like to go with you; however, my hands are full.
He hasn't arrived. He may, however, come later.
though:尽管，虽然．可以位于句首，句中．
...

but = 但是
最平常的用法，与汉语的“但是”用法差不多
例：
I wish I could sleep in but it was Monday.
though = 虽然
一般用于一个句子的中间或句末（区别于although——此词用于句首或句中）
例：
I didn't like the lecturer even though she...