however、nevertheless和but then怎么用?有什么区别?尤其是 however和but then都是连词对吧,什么时候用哪个啊?

but,however,still,nevertheless,yet这几个词的词义接近,都表示转折和让步.
（1）but用来引出微弱的相反的意见,是口语常用语,如：sally was amused,but i was very embarrassed.萨莉很开心,但我却很尴尬.
（2）however比but的词义还要弱些,并不直接引出相反的意见,因此常用作插入语,如：the most surprising thing about it,however,is that it can land anywhere.不过,答案〖but〗解析：关于这架飞机最使人吃惊的事情是,它可以在任何地方着陆.
（3）still还,还是,如：it is true that winter is over；still,it is almost as cold.冬天已经过去了,这是事实,但天气还是那么冷.
（4）nevertheless的含义为即使做出完全的让步,也没有任何影响,或者说也不是决定因素,如：there was no news；nevertheless,she went on hoping.一点消息也没有,但她仍抱着希望.
（5）yet的含义为即使做出极端的让步,也不会发生期待的结果,如：he worked hard,yet,he failed.他干得很卖力,然而却失败了.
a man who fears suffering is already suffering from what he fears.
害怕痛苦的人其实已经在承受他所害怕的痛苦了.