當我們要表達「原因」或「理由」時，英文最常使用的字就是because了。可是除了because之外，表達類似概念的還有because of、owing to、due to、as，以及since。
該如何使用這些字詞？它們之間的有那些差異？在這篇學習文章中，我們將一次告訴你！
各種「因為/由於」英文差異
Because是連接詞，後面必須接子句(主詞 + 動詞)。
例句
Ted couldn't join us because he had to work.
(Ted 沒能加入我們，因為他必須工作。)
Because Judy has done a great job at work, her boss gave her a big raise.
(因為 Judy 在工作上表現出色，她的老闆給了她一筆大幅度的加薪。)
As / since：連接詞
As與since也表達理由，不過它們比because來得正式，比較經常使用於寫作。
例句：
Since nearly everything can be done from home with computers and Internet, there is no need to dress up for work anymore.
(由於幾乎所有事情都能透過電腦和網路在家完成，現在已經不再需要為了工作而穿著正式了。)
As it was getting late, Tom decided to book into a hotel.
(因為天色已晚，Tom 決定投宿飯店。)
補充：如果我們要在問句中提出原因的話，我們只能使用 because，而不是 as 或 since。
例句：
Is Susan leaving early because her ex-boyfriend is here?
(Susan 是因為她的前男友來了，所以提早離開嗎？)
錯誤：Is Susan leaving early as/since her ex-boyfriend is here?
Because of / as a result of：介系詞片語
Because of與as a result of也表達理由，不過它們是介系詞片語，後面必須接名詞片語，而不能接子句。
例句：
The soccer match was stopped because of the rain.
(那場足球賽因為下雨而中止了。
Largely because of climate change, our global food systems are under considerable stress.
(主要是因為氣候變遷，我們的全球糧食系統正承受相當大的壓力。)
As a result of the pilots' strike, all flights have had to be canceled.
(由於飛行員罷工，所有航班都不得不取消。)
Extreme weather events are likely to be more frequent as a result of climate change.
(由於氣候變遷，極端天氣事件可能會變得更加頻繁。)
錯誤：Amy almost missed her flight because of there was a long line in the duty-free shop.
Due to / owing to
Due to與owing to也表達理由，後面必須接名詞片語，而不能接子句。
Due to a broken propeller, the cruise liner returned immediately to port.
(由於螺旋槳損壞，這艘郵輪立即返航。)
Owing to a lack of funds, the project will not continue next year.
(由於資金不足，這個專案明年將不會繼續進行。)
有些文法學家或寫作手冊認為，due與owing是「形容詞」，所以due to / owing to只能用來修飾名詞，而不能修飾動詞。
根據他們的主張，下面的句子是錯誤：
(X) The flight was delayed due to bad weather.
(X) The flight was delayed owing to bad weather.
下面的句子才是正確：
(O) The flight was delayed because of bad weather.
(O) The flight delay was due to bad weather.
(O) The flight delay was owing to bad weather.
可是根據韋氏字典，due to / owing to作為介系詞片語修飾動詞的用法，不僅可以回溯到十四世紀，而且在現代英文裡也廣泛地被母語人士使用。
其它字典(包括劍橋，牛津，朗文)也將due to / owing to標示為介系詞片語，並且列有它們修飾動詞的例句。
因此，我們認為due to / owing to在多數狀況下，可以跟because of互相替換使用。
那麼在哪些情況下，due to / owing to 不適合與because of替換使用呢？與because of相比，due to / owing to比較正式，通常出現於寫作，尤其owing to經常出現於正式公告或官方通知中。因此，下面的句子，對母語人士而言聽起來會有點奇怪：
Owing to the heavy rain, we had to give up the idea of a boat trip.
(由於大雨，我們只好放棄搭船出遊的念頭。)
主要子句的訊息與詞彙，都是偏向口語的表達方式，可是說明原因時，卻是使用偏正式的表達方式。比較自然的說法，應該是：
We had to give up the idea of a boat trip because of the heavy rain.
練習選擇正確答案。
1. The country's investment is falling, likely in part ______ the higher cost and lower availability of financing.
(A) due
(B) owe to
(C) a result of
(D) because of
解析
根據句構，空格後面是名詞片語(the higher cost and lower availability of financing)，所以空格裡需填介系詞片語，所以答案為(D) because of。整句話的意思是：這個國家的投資正在下滑，部分原因可能是成本上升及取得資金的難度提高。
2. The increase in childhood obesity is largely ______ changes in lifestyle and diet over the last 20 years.
(A) since
(B) due to
(C) because
(D) as a result of
解析
根據句構，空格後面是名詞片語(changes in lifestyle and diet)，所以空格裡需填介系詞片語，所以答案為(B) due to。整句話的意思是：兒童肥胖率的上升，很大程度上是由於過去二十年來生活方式與飲食的改變。
3. Many test-takers lose marks simply ______ they do not read the questions properly.
(A) due
(B) because
(C) owing to
(D) as a result of
解析
根據句構，空格後面是子句(they do not read the questions properly)，所以空格裡需填連接詞，所以答案為(B) because。整句話的意思是：許多考生只是因為沒有正確閱讀題目而失分。
結論
本篇學習文章說明because、because of、owing to、due to、as、since這些字詞的用法與差異。如果學員想完整學習英文文法，我們推薦巨匠美語的文法課程。巨匠與專業的文法老師合作，將文法結合聽說讀寫等課堂遊戲，讓你用有趣的方式，有效率地學習英文文法。
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