轉折詞後面須有逗點，但前面絕不可有逗點

• John was ill. As a result, he could not come. (約翰病了，所以他不能來) (正)
• John was ill; as a result, he could not come. (正)
• John was ill. As a result he could not come. (誤)
• John was ill, as a result, he could not come. (誤)

解說：英文常用的轉折詞 (transitional phrases) 有 however, therefore, consequently, nonetheless, nevertheless, as a result 等。這些轉折詞後面須有逗點，但前面絕不可有逗點 (前面要用句點或分號)。