導語：非限定性定語從句起補充說明作用，缺少也不會影響全句的理解，它與主句往往用逗號隔開。下面小編講解which非限制性定語從句，歡迎參考。
■關係代詞which只用於指事或物，不用於指人，它在定語從句中主要用作主語或賓語。如：
She was not on the train which arrived just now. 她不在剛纔到達的那列火車上。(關係代詞which指train，在從句中用作主語)
He never got back the money which he had lent him. 他從未收回他曾借給他的那筆錢。(關係代詞which指money，在從句中用作賓語)
■which用於引導限制性定語從句外，還可以引導非限制定語從句。如：
The ship struck an iceberg, which tore a huge hole in her side. 船碰在一座冰山上，船幫被撞出一個大洞。
She gave me this jumper, which she had knitted herself. 她送給我這件羊毛衫，這是她親手織的。
This machine, which I have looked after for twenty years, is still working perfectly. 這臺機器我已經照管了20年，現在仍然沒一點兒毛病。
■which有時也可用作定語，尤其用於“介詞+which+名詞”這類結構中，此時的which含有this或that的意味。如：
He may be busy, in which case I’ll call later. 他可能忙，如若如此，我以後再來拜訪。
I may have to work late, in which case I’ll telephone. 我可能得晚點下班，那樣我會打電話的。
He lost his temper, at which point I decided to go home. 他發脾氣了，這時我就決定回家了。
He was appointed Lord Chancellor, in which post he spent the rest of his life. 他被任命爲大法官，在這個職位上度過了他的`後半生。
The postman comes at 6.30 in the morning, at which time I am usually fast asleep. 郵遞員早晨6點30分來，這個時候我通常還睡着大覺呢。
It was derived from Posidonius, for which reason much of its information may well have been out of date. 它源於鮑森杜尼爾斯。由於這個原因，它的大部分信息很可能已經過時。
有時其前也可以沒有介詞。如：
He is studying economics, which knoweledge is very important today. 他學經濟學，這種知識現今很重要。
He spoke in Greek, which language I could only follow with difficulty. 他說希臘語，我聽起來很吃力。
■ 關係代詞which有時可用於指人。原則上說，which用於指事物，不用於指人。但以下情況屬於例外：
1. 用於在指人的名詞之後，指不強調性別的嬰兒：
He was the last child which was born. 他是最後出生的孩子。(which指小孩)
2. 當不是指具體的某人，而是指人的屬性（如職業、身份、地位、職務、品質、特徵等）時，則也用關係代詞 which而不用 who。如：
They accused him of being a traitor, which he was. 他們指控他是叛徒，他真是叛徒。
She talked like a native, which she hardly was. 她說起話來像是個本地人，其實她不見得是。
■ 在非常正式的文體中，代詞that後可以接一個修飾它的定語從句，這個定語從句通常用which來引導。如：
They say the only real knowledge is that which can be measured. 據說唯一真實的知識是可以檢驗的知識。
在現代英語中，that which通常用what來代替。如：
We have that which (=what) we need. 我們需要的東西都有了。
That which (=What) many people say is not always true. 很多人說的話並不表示一定是真的。
