在定语从句中什么时候用which 什么时候用介词+which？

观察下面句子：the house which i visited is beautiful.我参观的房子很美
The house in which i live is beautiful.我住的房子很美。
都是定语从句，先行词是名词或者代词，第一句用which，第二句用in which，主要的原因在于从句谓语. visit sp. visit是及物动词，visit the house 即可，which指代先行词the house. 而第二句，live 不及物，表达方式应为live in the house 所以变为live in which， in which 提前就变成这样了。

另外还有些，
譬如The reason why (=for which) i am late is ..... ----i am late for the reason（which=the reason）. 为了这个原因我迟了。
The factory where (=in which) i worked is big. work in the factory
The spring festival, when (=during which) all the family members will get together, is wonderful. ---members will get together during the festival. 介词一定要加，不然句子不通。

同理，where, when, why=介词+ which
不知道你懂没

其实原则很简单，就看which所代表的先行词在句中做什么成分，如果是主语宾语补语什么的就不用+which了，例如The planet which supports a great many Avantars doesn's exist at all中which所指示的先行词plannet做的事定语从句中的主语就不用介词+which了。但是The planet from which a great many Avantars are supported doesn't exist at all 中的的先行词planet在定语从句中做的是状语，只有from which整体才能使句子完整。
所以得看关系词which或者介词+which在句子做的什么成分。
希望能帮到你

用which 是指代前面所提到的人或事件，可作为主语。用介词+which 则是做为状语或其他成分。比如：in which 就相当于where ,引导地点状语从句，understand ?

看修饰的词，比如we solve the problem in the way= the way in which we solve the problem

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