介词加关系代词(介词加关系代词都等于哪些词

“介词加关系代词”等于另外一个词，是出现在定语从句中的一种现象。“介词+关系代词”起一个关系副词的作用，相对于一个关系副词。

in/on/at/during/…+which=when

in/on/at/…+which=where

for+which=why

例句：

1. This is the factory in which he worked.

这是他曾经工作过的工厂。

in which=where

2.This is the farm on which he worked.

这是他曾经工作过的农厂。

on which=where

3.This was the reason for which he was late for school.

这是他为什么迟到的原因。

for which=why