幾個英文字的分別

在詞性上，它們都可以作為adverb，並conjunction用，但but還可以作前置詞(preposition)和關係代名詞用(relative pronoun)，除了它們詞性分別，我們現在談到它們意義的分別
其實nevertheless與nonetheless是沒有分別，甚至牛津字典（第四版）給nonetheless的解釋就是nevertheless，但nevertheless比nonetheless就更formal；至於這兩個字與but的分別是甚麼，若我們看中文的解釋，可能有點不大能分別，但英文的解釋就比較清楚
nevertheless／nonetheless的解釋是：despite what has just been said or done:
(雖然如此）
e.g. There are serious problems in our country. Nonetheless, we feel this is a good time to return.（在我們的國家還有很多嚴重的問題，雖然如此，我們覺得這是我們返國的好時機）

至於but的意思與nevertheless的意思分別也不大，在牛津第四版就給予它其中有這樣的解釋：inspite of this; however等等，然而but還有好幾種的解釋與用法
１）used to introduce an added statement, usually something that it different from what you have said before:（用來引進另外一句的陳述，而這句陳述是與你先前所說是有分別的）
e.g. She's very hard-working but not very imaginative.

２）except（除了）:
e.g. Eventually, all but one of them promised to come to his leaving party.
e.g. He's anything but violent (= not violent in any way).
３）ONLY（只是）
She's but a young girl!
縱觀我們以上分析，除了but的用法與意思比較多外，nevertheless比nonetheless比較formal外，它們其實是沒有太大分別，是可以互相代用。
在此一題，nonetheless其實是來自none the less，而nevertheless也可以看作never the less，它們的發音也是none the less，與never the less

至於thereby同therefore的分別，就比較清楚
thereby的意思是：by that means藉此，（意思是藉著前面所提及的事，能達到某些目的）
e.g. They paid cash, thereby avoiding interest charges.

paid cash是達到avoiding interest charges的手段

而therefore的意思：for that reaso因此，為此
e.g. He was down with the flu, and therefore couldn't come to the party.
他患了流行性感冒,因此未能前來參加宴會。

down with flu是couldn't come to party的原因


所以我們看到thereby之前所提的是它以後目的的途經，是intentional
而therefore之前所提是它以後結果的原因，是因果性，或是事實性

希望你明白我的解釋

nevertheless

仍然,不過,然而
She was angry; nevertheless, she listened to me.
她很生氣,但還是聽了我的話。
We can't act on your advice. Nevertheless, thank you for giving it.
我們不能照你的建議去辦。不過承蒙您提出來,十分感謝。

nonetheless

ad.
1. 但是;仍然
conj.
1. 但是;仍然

nonetheless = however
Example:
There are serious problems in our country. Nonetheless, we feel this is a good time to return.

but

1. 但是
It is hot in summer here, but it is not cold in winter.
這裡夏天熱,但冬天不冷。
2. (通常用not...but...)而是
Our purpose is not to do it for you but to teach you to do it by yourself.
我們的目的不是替你做這事,而是教會你自己來做。

thereby

1. 因此,由此,從而
He wished to travel and thereby study the customs of other countries.
他希望去旅遊藉此研究其他國家的民俗風情。
2. 在那件事上
3. 【古】在那附近
His home is hidden in the trees thereby.
他的家就在那附近的樹林之中。

therefore

1. 因此;因而;所以
He was down with the flu, and therefore couldn't come to the party.
他患了流行性感冒,因此未能前來參加宴會。