conjunctive adverb 的正確用法

首先，我發現Dr.eye 例句上有很多錯誤


http://www.nciku.com.tw/search/en/detail/nevertheless/51476

這線上字典比較正確

維基百科的清楚說明
http://en.wikipedia.org/wiki/Conjunctive_adverb


無論是however或是nevertheless，都只能當副詞，不能是連接詞，當然也不等於but。雖然有人稱他們為"連接副詞"，但只代表語意上有連接的意思，他們還是副詞，不能用來連接兩個句子!無論單雙逗號都不行!

副詞若要插入句子裡作補充描述，要碼放句首句尾，要碼前後都要有逗號，而且只能用在單一句子裡面。例如:
I am handsome.      However, I am poor.
I am handsome.      I am, however, poor.
前面句子必須用句號結尾，然後再"另啟新句"，用副詞however表達"然而"。
nevertheless和however都是連接副詞，語意上可能略有不同，但在句子裡的用法完全相同。

補充說明:只有連接詞能連接兩個句子，例如: I am poor, but I am happy.  用副詞連接兩個句子，否則就是犯了 Comma splice 文法錯誤。你舉的例句都有 Comma splice 錯誤。

關你犯的文法錯誤(however, nevertheless)，wikipedia上有也有特別解釋:
According to Joanne Buckley, comma splices often arise when writers use conjunctive adverbs to separate two independent clauses instead of using a coordinating conjunction. A coordinating conjunction is one of the following seven words: for, and, nor, but, or, yet, so. A conjunctive adverb is a word like furthermore, however, or moreover. A conjunctive adverb and a comma (or a conjunctive adverb between two commas) is not strong enough to separate two independent clauses and creates a comma splice. For example, "There is no admission fee, however you will be responsible for any food you order." contains a comma splice with a conjunctive adverb.

for做連接詞的用法:
因為,由於

We must start early, for it will take two hours to drive to the airport.
我們得早點動身,因為開車去機場得花兩個小時。


Yet做連接詞的用法:
可是,卻,然而
I don't know him, yet I can get his help.
我不認識他,但我會得到他的幫助。



 for, and, nor, but, or, yet, so之外也可以做連接詞的


either....or, neither.....nor, not only......but also, both......and

參考資料:
韋氏字典
nevertheless: http://www.merriam-webster.com/dictionary/nevertheless
however: http://www.merriam-webster.com/dictionary/however

Wikipedia
Comma splice: http://en.wikipedia.org/wiki/Comma_splice