定语从句中“介词+which”与“which”的用法区别如下：
一、基本规则
限定性定语从句 引导词用 that
，且 不能省略。 - 例如：
> The book that I borrowed from the library is very interesting.
（等同于：The book which I borrowed from the library is very interesting.）
非限制性定语从句 引导词用 which
，且 必须用逗号与主句隔开。 - 例如：
> The movie, which was released last year, won several awards.
（等同于：The movie that was released last year won several awards.）
二、介词与which的搭配
介词+which： 引导非限制性定语从句，替代整个分句，作主语或宾语。 例如： > The company, in which we worked, is now a multinational corporation. （等同于：The company that we worked in is now a multinational corporation.） 介词后接关系代词 指人时用 whom
> The person whom I met at the conference is my old friend.
（等同于：The person which I met at the conference is my old friend.）
三、注意事项
介词位置
介词需置于关系代词之前，且不可省略。例如：
> The letter which arrived yesterday was from my aunt.
（不能写成：The letter arrived yesterday which was from my aunt.）
替代作用
介词+which可替代整个主句，避免头重脚轻。例如：
> The project, which required extensive research, was finally completed.
（比直接使用主句更简洁）
与that的区别 ： 限定性定语从句中，which和that可互换，但非限制性定语从句只能用which。 - 例如：
> The book that I read is fascinating.
（不能写成：The book which I read is fascinating.）
四、常见错误
省略which
非限制性定语从句中which不可省略，否则会导致句子结构混乱。例如：
> The movie which won the award is very popular.
（正确）
混用that和which：
限定性定语从句只能用that，非限制性定语从句只能用which。
通过以上规则和注意事项，可有效掌握定语从句中介词+which与which的用法。
