1、However, but, yet, while, whereas 表转折的区别
表示转折关系的并列连词
- however: 然而，不过。位置句首、句中，用逗号隔开；语气比but 弱，不直接引出相反意见。用作副词较常见。
I’d like to go with you, however, my hands are full.
He said that it was so; he was mistaken, however.
He apologized to me. However, I didn’t forgive him.
- but: 但是，用来引出相反意见或不同情况，常用于口语中。连接两个并列的成分或句子，语气较强，在意义上构成明显的对比。与前分句可用（可不用）逗号，与后分句不用逗号。
I’d asked everyone but only two people came.
It is cold in summer here, but it is not cold in winter.
It was a sunny but not very warm day.
She wanted to go swimming, but her parents told her not to.
I ought to have helped her, but I never could. 我本该帮她但没能。
Honey is sweet, but the bee stings. 蜂蜜很甜，但蜜蜂有刺蜇人。
- yet: 作连词时，“然而，可是，却，而”，与but相比，比较的意味较强，经常以and yet形式出现。
It’s a small car, yet it’s surprisingly spacious.
It’s freezing cold. Yet you have to go out, don’t you?
I don’t like him, and yet I have to work with him.
He said he was our friend, yet he wouldn’t help us.
- while: 并列连词时，while conj. 然而 = whereas 表示对比或用于引出相反的情况。只强调两者之间的对比，并不强调转折。并列句、且两个句子谓语动词同时发生或结构相同。
You like playing tennis, while I like reading.
I earn only 80 dollars a week, while she earns 100 dollars.
Some men are rich while others are poor.
Jane is slender while Mary is stout. 简苗条而玛丽强壮。
Motion is absolute while stagnation is relative. 运动是绝对的，而静止是相对的。
There’s plenty of rain in the southeast, while there's little in the northeast.东南部雨量充足,而西北部则很少下雨。
Some people waste food while others haven't enough.有些人浪费粮食,然而有些人却吃不饱。
- 注1：but 一般不可与 yet, however, nevertheless 等连接性状语连用，但可以和on the contrary, on the other hand, still 等连用。
She tried again and again, but still, she didn’t succeed. 他一遍又一遍地尝试，但仍然没成功。
- 注2：表示转折概念的词：
still, yet, however, nevertheless, on the other hand, on the contrary, conversely, all the same, though, after all, for all that, in the meantime等词语。这些词在本书中都作为连接性状语处理。
- 注3：一句话区别：
but 口语常用词，语气较强，泛指与前述情况相反，放句中。
however 表转折关系，语气稍弱于but，连接性也弱一些，因而常作插入语，放句中，常常在前面用逗号。
still 语气强，多用于肯定句或疑问句。指尽管作出让步，采取措施或表示反对，但情况仍然如故，无所改变。
yet 常用于否定句，语气比still稍强。指不管作出多大努力或让步，仍达不到预期的结果。一般放在句末,前面一般不用加逗号。
nevertheless 指尽管作出完全让步，也不会发生任何影响。
while 表对比，一般可与whereas换用，但程度弱一些。
whereas 表对比，一般可与while互换。
- 注4：only 用作表示意义转折的并列连词，只见于非正式文体。
You may go, only come back early. (only =but) 你可以走，但要早点回来。
He wants to buy the watch, only he can’t afford it. 他想买这块表，但他买不起。
- 注5：however 释义
adv. 无论如何；不管怎样 However hard it may be, do your best.
adv. 尽管如此；然而 Later, however, he decided to go.
adv. (表示惊奇)怎样；怎么 However did you find it? 你是怎样找到它的？
conj. 不管怎样；不管用什么方法 He can go however be like.他想怎么去都行。
2、whereas与while的区别
1.whereas = while
while前后句子之结构要求并列相对，whereas 在结构上则不一定不需要严格平行。（OG12-131）
whereas/while这种连词连接的比较成分不要求含义上绝对的平行
2.whereas连接的平行比较只要求对比的核心逻辑上有对称关系，不要求对称位置必须是对称名词，下面句子中主从句的主语分别是energy和nuclear power并不是对称名词，但是对比的核心都是“核能发电占总产出能量的份额”，如OG12-131:
Over 75 percent of the energy produced in France derives from nuclear power, whereas nuclear power accounts for just over 33 percent of the energy produced in Germany.
*：
- 但是如果whereas后面接介词短语，那么主句的开头也必须需要是介词短语(whereas后出现介词短语或者状语都会非常对称)如OG-113：
Whereas in mammals the tiny tubes that convey nutrients to bone cells are arrayed in parallel lines, in birds the tubes form a random pattern.
- 如果whereas后接单纯主谓宾（或主系表），主句也要尽量用单纯的主谓宾（或主系表）来对应，如prep08 194:
Whereas the honeybee’s stinger is heavily barbed and cannot be retracted from the skin, the yellow jacket’s stinger is comparatively smooth, and can therefore be pulled out and used again.
3.while 引导的从句:
1)意思是“当…时”，放句首或句中
2)意思是“转折对比contrast”时，多放在句中，也可以放在句首。while表示对比概念的时候，两个事物要是同时发生（但是while本身并没有at the same time的意思，所以while at the same time是可以prep 1-96）。
3)意思是“虽然、尽管”（让步）时，多放在句首。(=although)
4)表示条件,意为"只要",其意思和用法相当于as long as。while可位于句首,也可位于句中。
*：While放在句中时要特别注意，像OG12-131的A选项，ETS说while 放在中间表示“同时发生”的意思大于对比的意思。
Over 75 percent of the energy produced in France derives from nuclear power, while in Germany it is just over 33 percent.
2.1、更多例子：
从属连词whereas意为：“然而，但是，反之”（but, in constrast, on the contrary, while）用于陈述相反的话，引出表示对比、对立或直接相反（Direct Opposition）的状语从句，是正式用法，语气强并且书卷气较重，通常多位于居中，也可置于句首；通常多用逗号隔开，也有语法学家和某些权威词典主张不用逗号。如
（3）His parents were rich, whereas mine had to struggle.
（4）Many small birds use new sites for each nesting, whereas large birds often reuse the same nest.
（5）Whereas it is day with us, it is night with the Americans. (=It is day with us, whereas it is night with the Americans.)
应该注意的是whereas引导的从句与主句在意义上不仅是对立和相反的，而且也是并列的（因此也有人认为whereas是并列连词），两者可以互换，无论主句在前，还是从句在前，其句意都不变。如
（6）Old people in my country usually live with their children, whereas the old in the United States often live by themselves. (=Whereas old people in my country usually live with their children, the ole in the United States.)
即使主句和从句改变词序，其实际意义也大体相同。如：
（7）They want a house, whereas we would rather live in a flat. (=Whereas we want a flat, they would rather live in a house.)
那么，whereas 与while可以换用吗？两者有何区别呢？
同样，while也可意为：“（然）而，但是，反之”（but, whereas）,也可引出表示对比或相反情况的状语从句，相当于whereas，两者通常可以换用，但不如whereas正式，语气也不如whereas强,是普通用语，更为多用。如：
（8）They spend all their money on their house, whereas(while) are prefer to spend ours on traveling.
（9）While(Whereas) some newspapers have no advertising at all others carry many advertisements.
与whereas一样，主句和从句之间通常也用逗号隔开，但也可不用。如
（10）That region has plenty of natural resources while this one has none.
同样，也有人将while看作并列连词。顺便说一下，whilst 与while 同义，但比while正式，尤其多用在英国英语中，如：
（11）Raspberries have a matt, spongy surface whilst blackberries have a taut, shiny skin.
最后，where作连词用时，也可意为：“（然）而，反之”（but, whereas）,引出表示对比或与主句意思相反的状语从句，相当于意思接近于whereas和while，但通常多用于口语，而whereas是正式用法，多用于书面语（但有时也可用于口语）。如句（７）中的whereas可换用where而意思不变。又如：
（12）Some people spend their spare time reading, where others watch television.
（13）She is very diligent, whereas(while, where) he is very lazy.
值得注意的是whereas和while也可引出让步状语从句（adverbial clause of concession, 意为：“虽然，尽管”（although）,多位于句首，比较文气。如：
（14）Whereas the amendment is enthusiastically supported by a large majority in the Senate, its fate is doubtful in the House.
（15）While I admit that there are problems, I don’t agree that they cannot be solved.你的问题或可得到解决。
参考：
http://blog.sina.com.cn/s/blog_149f8478a0102x16g.html
https://forum.chasedream.com/forum.php?mod=viewthread&tid=770110&page=1&fid=23&showoldetails=yes
http://blog.sina.com.cn/s/blog_4c100dc80100vvrz.html