定语从句中的关系副词有三个：when, where和why，它们在定语从句中分别作时间、地点和原因状语。其句法结构如下：
1. when指时间，在定语从句中作时间状语。
例句：I still remember the day when I first came to Beijing.
I’ll never forget the day when I joined the army.
2. where指地点，在定语从句中作地点状语。
例句：The factory where his father works is in the west of the city.
This is the house where I lived two years ago.
关系副词“when”、“where”既可引导限制性定语从句，也可引导非限制性定语从句。
例如：I will always remember the day when I first visited the Great Wall.
He came to Shanghai in 1980, when he was only 12.
I don’t know the exact spot where they will meet.
Mr Wang will fly to Beijing, where he will stay for three months.
有时关系副词“when”、“where”引导的限制性定语从句和先行词有间隔的现象，是为了平衡句子的语法需要。
Do you remember one afternoon ten years ago when I came to your house and borrowed a diamond necklace?
The days are gone forever when the Chinese people used “foreign oil.”.
3. why只用于reason之后的限制性定语从句中,在定语从句中作原因状语。
例句：That is the reason why I did the job.(在现代英语中why可以省略)
上句也可以这样表示：
That is the reason I did the job.
又如： This was the reason (why )we raised the temperature.
关系副词在定语从句中的用法看似简单，以下注意点不可忽视：
1）“when”、“where”和“why”的运用取就于表时间的名词、表地点的名词和表原因的名词reason在定语从句中所作的成分，比较下面的几组句子：
*I will never forget the day when I first met you on the seashore.
*I will never forget the days which/that we spent together in Xueyao Middle School.
**This is the hospital where my mother works.
**This is the hospital which/that we visited the day before yesterday.
***The reason why he did not go to school is that he was ill.
***This is the reason which/that he gave his boss in the office .
2) “when”、“where”和“why”都可以替换成“介词 + which”，介词的选用取就于先行词和定语从句中的动词。例如：
Do you still remember the day on which we first met in Nantong?(on which=when)
This is the room in which we lived last year.(in which=where)
Do you know the reason for which he refused to go to Mary’s birthday party. (for which=why)
英语中的关系副词由：where,when和 why。这三个关系副词很多情况下，都可以用介词+关系代词来替换。
where=in /at /to+which;
when=in /on /at+which;
why=for +which.
有时定语从句中介词短语和动词有意义紧密的修饰关系，尤其在非限制性定语从句中，常使用“介词 + which”结构，而不使用关系副词。例如：
My mother works in a factory, in front of which there is a small river.
At night the soldiers got to a small hill, at the foot of which stood a farmhouse.
3) “that”可活用为关系副词，相当于“when, where、why”和“介词 + which”结构，尤其在“the time when”等结构中的“when”常被“that”代替，而且“that”往往省略。
I may leave here any time I want to.
During the time I was there I visited him twice.
This is my second time I have come to your country.
1.It’s helpful to put children in a situation they can see themselves differently.
A. that B. when C. which D. where
答案 D
解析 考查定语从句。先行词是situation，指物，亦可指地点，关系词在从句中做地点状语，用关系副词where，选D。
2. I have reached a point in my life ______ I am supposed to make decisions of my own.
A. which B. where C. how D. why
答案 B
3 .After graduation she reached a point in her career she needed to decide what to do.A.that B.what C.which D.where
答案 D
解析 本题考查定语从句关系词的确定。英语中，point/situation/case等作先行词，其后的关系词在定语从句中作状语时，用关系副词where（相当于in which）。该定语从句缺少地点状语，因此用where。
4.Life is like a long race _____we compete with others to go beyond ourselves.
A. why B. what C. that D. where
答案 D
5.Occasions are quite rare I have the time to spend a day with my kids.
A.who B.which C.why D.when
答案 D