When,where,why引导定语从句四注意（一）
1.先行词表示时间、地点、原因，但关系词指代先行词在定语从句中充当主语或宾语时，应用关系代词that或which.如：
Ill never forget 1976 that / which was full of sadness.
（作主语）
我不会忘记充满悲哀的1976年。
I regret the days （that/which） I wasted in the woods.
（作宾语）
我后悔在森林里虚度的日子。
This is the factory that/which produces cars. （作主语）
这就是那个生产小汽车的工厂。
This is the factory （that/which） he visited yesterday.
（作宾语）
这就是他昨天参观的工厂。
This is the reason that/which is unreasonable. （作主语）
这是一个没道理的理由。
This is the reason （that/which） he raised. （作宾语）
这是他提出的理由。
2. 关系副词有时相当于 适当的介词+关系代词。如：
① where=in/on which
This is the room where / in which he lives.
这就是他住的房间。
I can see the desk where / on which there is a book.
我能看见上面有一本书的那张桌子。
② when= on/in/at which
I still remember the year when/ in which I joined the Party. 我仍然记得入党的那一年。
I still remember the day when/on which I joined the Party. 我仍然记得入党的那一天。
I still remember the date when/at which I joined the Party. 我仍然记得入党的那个日子。
③ why=for which
This is the reason why / for which he was killed.
这是他被杀害的原因。
3. 当先行词为time表示 次数时，常用关系词that或省去关系词，而不用when来引导定语从句。如：
This is the first/last time that I shall give you a lesson.
这是我第一次/最后一次给你们上课。
4. 当point，situation等词作先行词表抽象的地点，其后常由where引导定语从句，where在定语从句中作地点状语。
Can you think out a situation where this word can be used？ 你能设想这个单词被使用的场合吗？
Her illness has developed to the point where nobody can cure her. 她的病发展到没人能治的地步。[1][2]