previous与before的区别

efore 作 介词,连词,或者副词.
介词：可在后加一个时间点或者短语.如 before 6 o'clock.
连词：连接句子.she had finished homework before we went shopping.
副词：作为状语.I’ve never been there before.
previous 形容词 作定语的.修饰名词.a previous suggestion 一个预先的迹象
before作副词时同previously.但是before偏重于 之前 先前的意思.previously偏向预先的意思.

previous 上一个
before 之前
before 大致等于 previously，但两个词用法不同。