濫竽

1. 文法

But 在文法上是一個連接詞，即用來連接兩句完整句子的字；但 however 只是個 adverb，不能用來連接句子。而用 however 時要用 comma 把它從句子其他部份分開。簡單例子：

I love her, but she doesn't love me.

這裡如果換上 however 就錯了文法。要開新句才可用 however：

I love her. However, she doesn't love me.

如果兩句句子意思緊接，你想用 however 卻不想把它分開兩句，可以用分號 "；"：

I love her; however, she doesn't love me.

至於 but 可否放在句前呢? 現在越來越多人這樣寫。老一輩的文法專家說不；但新一代較為開明的英文學者認為 but 用於句子開頭表達意思明確而直接，反而值得鼓勵。

2. 用法

這 是最重要的分別。However 可用於句子中間，用作加強語氣的 interruption。其實這才是 however 最好用的地方。英文寫作專家 William Strunk 在其巨著 "The Elements of Styles" 寫道：永遠不要把 however 放在句子開頭 (however 另外一個用法除外)。

例句：

(i) Abortion is outlawed in many European countries. Illegal abortion, however, is thriving.

(ii) It is clear, however, that...

(iii) Many people welcome the newly introduced smoke ban; restaurants owners, however, were pissed.

(iv) Most people believe that abc. Researches have shown, however, that xyz.

那 麼 however 要放在句子甚麼位置? 理論上句子裡任何位置都可以。規則是，放在你想強調的部份前面。在例句 (i) 和 (iii)，我認為 contrast 最明顯的地方是動詞 "is thriving" 和 "were pissed"，就在前面加上一個有點兀突的 however。這樣，對比的感覺會特別強烈。However 最常見的位置是在修飾整句的 adverb 後："I kept asking her out and she kept refusing. At last (adverb), however, she agreed to go out with me."。另外一個常見的位置是句子主語 (subject) 和動詞中間，像例句 (i) 和 (iii)。最後，如果句子有 that 的話，可以放在 that 之前："It is clear, however, that..."；"He said, however, that..."。

還有要留意，如果 contrast 重點在句子動詞，而動詞有 modal 在前的話 (may, should, can, etc)，通常 however 會放在 modal 和動詞中間："should, however, do sth".

3. 讀音語氣

家 常談話通常會用 but，而 however 這個三音節的字通常只用於書面或較正式的對話。還有一點要留意，however 在一句句子裡通常是語氣上的重點，會把讀者對這句句子的注意力都搶了過來；相反，but 可以是個無關痛癢，可輕輕帶過的字。選用的時候就要想一想：到底這個 contrast 是否句子的重點?

用好 however 這個字，句子會好看得多。想清楚句子意思才用吧。

However 還可解作 "It doesn't matter how..."。這個用法完全不同，有機會再和大家詳談。