◇ Participle Clauses
分詞構句
The purpose of participle phrases is to simplify a sentence. When the subject is repeated, the conjunction and subject will be removed, and the verb will be changed to the form of a present or past participle. The clause that is turned into a participle clause is usually the one in the sentence that expresses "condition, reason, result, or an earlier event". The sentence "It (the virus) pretends to be a friend, and it attaches to a projection on the cell membrane." "The virus" is a common subject, so the conjunction is deleted and the verb is changed to present participle "pretending", forming the participle clause that describes an earlier event.
分詞構句目的在於精簡句子。首先確定兩句主詞相同，接著移除表示「原因、條件、結果」的從屬子句的連接詞與主詞。若刪去的主詞「主動」執行該句的動作，則將動詞改為帶有主動意味的現在分詞；若未執行該句的動作，則改為「被動」意味的過去分詞。Pretending to be a friend, it (the virus) attaches to a projection on the cell membrane. 正是分詞構句，若將其還原我們可以得到 "It (the virus) pretends to be a friend, and it attaches to a projection on the cell membrane."。由於 it 是主動執行動作，因此我們刪除連接詞，將 pretends 改為現在分詞 pretending。
Example：
1. Seeing the police coming, the thief quickly ran away.
一見到警察來，小偷就快速地跑走了。
2. The thief is running on the street, chased by policemen.
小偷被警察追捕而在街上逃跑。
3. Having lived in Seattle for fifteen years, John loves this city.
John 在西雅圖生活了15年，因此深愛這座城市。