定语从句如何找先行词
怎么找出定语从句中先行词，然后怎么判断先行词做什么成份呢？有哪些技巧与方法？
先行词是名词或代词,如果名词或代词后面有修饰它们的句子且它们在句中充当某一成分,它们就是先行词.
把先行词还原到从句中,就能判断做什么成份.
如:I will never forget the day when I first went to school.(先行词是day)
从句=I first went to school on the day.
(on the day 在从句中作状语=when)
I will never forget the day that was veryecial to me.(先行词是day)
从句=The day was very special to me
(the day 在从句中作主语=that/which)
修饰定语从句的先行词有哪些，如何使用
一、关系代词（在句中作主语、宾语或定语）
1. that既可代表事物也可代表人，which代表事物；它们在从句中作主语或宾语，that在从句中作宾语时常可省略关系词，which在从句中作宾语也可以省略。[eg：this is the book （which）you want。]而且，如果which在从句中作“不及物动词＋介词”的介词的宾语，注意介词不要丢掉，而且介词总是放在关系代词which的前边，但有的则放在它原来的位置
2. which作宾语时，根据先行词与定语从句之间的语义关系，先行词与which之间的介词不能丢
3. 代表物时多用which，但在带有下列词的句子中用that而不用which，这些词包括当先行词是anything, everything, nothing , none等不定代词时，或者是由every, any, all, some, no, little, few, much等修饰时等，这时的that常被省略 还有先行词前有序数词或形容词最高级修饰时,或先行词就是序数词或最高级时.以及先行词中既有人又有物时.还有句中前面有which时,都只能用that
4. who和whom引导的从句用来修饰人，分别作从句中的主语和宾语，whom作宾语时，要注意它可以作动词的宾语也可以作介词的宾语
5. whose是关系代词，修饰名词作定语，相当于所修饰成分的前置所有格.它引导的从句可以修饰人和物, 当它引导的`从句修饰物体时, 可以与 of which 调换,表达的意思一样。
二、关系副词（在句中作状语）
关系副词=介词+关系代词
why=for which
where=in/ at/ on/ ... which (介词同先行词搭配)
when=during/ on/ in/ ... which (介词同先行词搭配)
1. where是关系副词，用来表示地点的定语从句。
2. when引导定语从句表示时间〔注〕值得一提的是，表示时间“time"一词的定语从句只用when引导，有时不用任何关系代词，当然也不用that引导。
By the time you arrive in London, we will have stayed there for two weeks. I still remember the first time I met her. Each time he goes to business trip, he brings a lot of living necessities, such as towels, soap, toothbrush etc。
3. 当从句的逻辑主语是some, any, no, somebody, anybody, nobody, something, anything, everything或nothing时，常用there is来引导
There is somebody here who wants to speak to you. 这里有人要和你说话。
