though(雖然) 亦可用although代替, 為副詞連接詞, 引導副詞子句, 修飾句中主要子句。我們因受中文『雖然……但是……』的影響, 而常將英文說成"Though (Although)...but..."的錯誤句構, 因為英文的文法中規定兩句之間的連接詞只能有一個, 而though (although)與but均為連接詞, 如此一來, 形成錯誤的雙重連接句子結構。故我們若用though (或although)時, 則but應予省略; 若用but時, 則though (或although) 就應省略。

例: Though he is rich, but he is not happy.   (╳)

　→Though he is rich, he is not happy. (○)

　= He is rich, but he is not happy.

　(雖然他很有錢，但他並不快樂。)

　Although she was sick, but she still went to school. (╳)

　→Although she was sick, she still went to school. (○)

　= She was sick, but she still went to school.

　(雖然她病了，但她仍然去上學。)

　→Even though it will probably rain tomorrow, but we will go fishing as scheduled. (╳)

　→Even though it will probably rain tomorrow, we will go fishing as scheduled. (○)

　(即使明天會下雨，我們還是要按照計畫去釣魚。)

"Because...so..." (因為……所以……) 亦是錯誤的雙重連接句構, 因為because和so都是連接詞, 故用because時, 就不能再用so; 而用so時, 則不可再用because。

例: Because he was once bitten by a dog, so he is now afraid of dogs. (╳)

　→Because he was once bitten by a dog, he is now afraid of dogs. (○)

　= He was once bitten by a dog, so he is now afraid of dogs.

　(因為他曾被狗咬過，所以他現在很怕狗。)

　根據上述說明, 可知本文三句亦可寫成:

It is generally accepted that junk food is not healthful, but American fast-food restaurants are popping up all over the world.

Americans like things done immediately, so they often order their food quickly at fast-food restaurants.

It's not polite, but it's efficient.