導語：關係代詞用來引導定語從句，它代表先行詞，同時在從句中作一定的句子成分。下面YJBYS小編介紹英語關係代詞的重點用法與辨析，歡迎參考!
1. 關係代詞的形式與用法
主要的關係代詞有 that, who, whom, whose, which, as 等。其中who, whom 只用於指人，which, as 只用於指物，whose, that 既可於指人也可指物。關係代詞在定語從句主要用作主語、賓語、表語或定語。如：
People who smoke cannot travel in certain parts of the train. 吸菸的人不能在火車的某些地方走動。
He is not a person whose promise you can build on.他不是那種你可以信賴他諾言的人。
They read us the stories which they themselves had written.他們給我們讀他們自己寫的.故事。
2. that 與 which的用法辨析
兩者都可指物，常可互換，但引導非限制性定語從句或直接放在介詞後作賓語時，通常只用which;當先行詞是much, little, none, all, few, every(thing), any(thing), no(thing) 等不定代詞或受其修飾時，通常用that，另外，當先行詞受the very, the only, the same 以及最高階和或序數詞(包括last, next等)等修飾時，通常都只用that。如：
He invited us to dinner, which was very kind of him. 他請我們去吃飯，這是他的好心。
He grasped at anything that might help him. 他試圖抓住任何對自己有利的東西。
There was little that the enemy could do but surrender. 敵人無法，只好投降。
This is the only reference book (that)I find useful. 這是我發現的唯一有用的參考書。
注：當關系代詞在定語從句中用作表語時，通常用that，另外當先行詞是一個既指人又指物的並列片語時，通常用that。
3. as與which的用法辨析
引導限制性定語從句時，在such, as, the same後只能用as，其他情況用 which;引導非限制性定語從句時，有時兩者可互換，但若位於主句之前，則只能用 as。如：
He is not such a fool as he looks. 他並不像他看起來那麼傻。
You must show my wife the same respect as you show me. 你必須像敬重我一樣來敬重我妻子。
As is known to all, smoking is harmful to one’s health. 眾所周知，吸菸有害健康。
注：as 引導的非限制性定語從句應與主句在意義上和諧一致，which無此限制。如：
He married Mary, as [which] was expected. 他娶了瑪麗，這是大家預料到的。
He married Mary, which was unexpected. 他娶了瑪麗，這讓大家感到很意外。(不用as)
