这个为什么是定语从句?This is the first time [that] I have been here.

这就是定语从句.不过是有点特殊.当先行词有time,day,place,reason,way等的时候,可以用that代替when或where或why或介词+which,口语中that 还可以省略.比如：I still remember the day (that) you went away I still r...