讲一下whlie ,when ,as ,since引导的句子有什么特征,怎么用?

在定语从句中where when 的用法：
(1)when 可以代替in/on which 引导时间定语从句.
例如 That was the year when he was born.
那是他出生的那一年.
Sunday is a day when people don't have to go to work.星期天是人们不用上班的一天.
（2）where可以代替in/on which 引导地点定语从句.
例如：Let's meet at the gate where you can see the panda.我们在能看到大熊猫的那个大门见面吧.
She is teaching at the university where her mother once studied.
她在她母亲曾经学习过的大学执教.
This is the birdge where you took photos.
这是你照相的那座桥.
When 可以用来引导定语从句,如：
He came last night when I was out.
也可以用来引导状语从句,如：
He heard the doorbell ring when he was eating his breakfast.
when引导的是定语从句时,其前面往往有一表时间的先行词,when引导的定语从句则对先行词起修饰作用；而当when引导的是状语从句时没有这种词
（定语从句牵涉的句法太多了.这在高中只是提到皮毛,在大学一年级老师会详细讲到）

一般来说，when和while是在“当...的时候”做辨析
when+时间点 或瞬时动词，while+时间段 或进行时
比较：because, since, as和for
1） because语势最强，用来说明人所不知的原因，回答why提出的问题。当原因是显而易见的或已为人们所知，就用as或 since。
I didn't go, because I was ...