◇ Reduced Relative Clauses
關係子句簡化為分詞片語
Relative pronouns in the nominative case are subjects of the verb. In this case, if we omit the relative pronoun, the verb following the relative pronoun should be changed to the form of a participle. For example, "Studies have shown that anywhere from 4-78% of alcohol used in cooking still remains after basic recipes." In this sentence, "used" modifies "4-78% of alcohol." Here, the relative pronoun is omitted. We can rewrite the sentence as "Studies have shown that anywhere from 4-78% of alcohol that is used in cooking still remains after basic recipes." When the relative pronoun (that/which) gets omitted, we change the verb "is used" into the participle, "used". When changing verbs into participles, we should see whether the verb is of active or passive voice. If it is of active voice, we change the verb into a "present participle" (Ving); if it is of passive voice, we change the verb into a "past participle" (Vpp).
關係代名詞省略時，要注意的事情。我們來看看句子：Studies have shown that anywhere from 4-78% of alcohol used in cooking still remains after basic recipes. 句中的 used 是用於修飾 4-78% alcohol，而關係代名詞則被省略了。所以其實這句原本應該是：Studies have shown that anywhere from 4-78% of alcohol that is used in cooking still remains after basic recipes. 當關係代名詞作為關係子句中的主詞，關係代名詞 that/which 省略後，其後的動詞型態也要有所變化，變成分詞。至於是要變成現在分詞（Ving）還是過去分詞（V.pp），就要看該動詞是否是被動態。如果不是被動的話，該動詞改為Ving；如果是被動，則保留Vpp的型態。
Example：
1. The knife used to cut the bread is different from normal knives.
用來切麵刀的刀子和一般的不同。
2. I need to revise the project according to the advice given by Mary.
我需要根據 Mary 給我的建議修改專案。
3. Adding salt to water increases the temperature needed to get to a boil.
鹽加入水之後會提高沸點的溫度。