关系副词引导的定语从句中,何时用where,why,when;何时用in,which

where代表前面的地点,作定语从句的地点状语。
when代表前面的时间，作定语从句的时间状语。
why代表前面的原因,作定语从句的原因状语。
代替where，when并不一定要用in which.有时要用on which, at which等。
如：The desk on which you have put some books is mine.你放书的那张桌子是我的。代替why 是要用for which.

你分析定语从句中的句子成分，缺状语才能用关系副词引导，然后再看先行词，根据先行词的意思判断引导词在定语从句中所作的到底是时间状语还是地点状语，还是原因状语。时间状语就用WHEN引导，地点状语用WHERE，原因状语用WHY.
将先行词代入 In which=in + 先行词仍通顺时，In which 可以与关系副词互换（只做时间状语或者地点状语）
比如先行词为a year 代入in which 变成in a year 便能代替when

先行词为表示地点的名词且在定语从句中作状语时用where,先行词为表示时间的名词且在定语从句中作状语时用when,先行词为reason且在定语从句中作状语时用why.关系副词的使用场合有两种：
1.定语从句中,主,谓,宾成分完整时.
He will remember the day when he joined the Party.
2.定语从句中,谓语动词为不及物动词时.
He will remember the factory where he worked ten years ago.
This is the reason why he was late for school.
如果定语从句中,谓语动词为及物动词时,它后面又没有宾语时,就要用关系代词.
He will remember the day which he spent togeher with us.
He will remember the factory which he visited last year.
This is the reason which he gave/explained for his being late for
school.
in which 引导定语从句,作状语.
He will remember the factory in which/where he worked ten years ago.
I don't like the way in which he spoke to his father.

从句中缺少状语的时候用,where表地点,why表原因,when表时间,
where=in which