含义上,前者是对先行词的补充说明,是不必要的,也就是说,如果去掉非限定从,原句的句意仍然成立;后者是先行词的必要修饰,如果去掉则原句不完整. 形式上,前者在先行词和从句之间加逗号,后者不加. 例如: 限制性定从:There is somebody who wants to speak to you.(若去掉从句,则变为:There is somebody.句意不完整.) 非限定从:My house,which I bought last year,has got a lovely garden.(若去掉从句,原句依旧成立.)