before和previous的区别是什么

Previous 多用作形容词，而before 是介词、连词、副词。

previous /ˈpriːvɪəs/ CET4 TEM4
1.ADJ A previous event or thing is one that happened or existed before the one that you are talking about. 前一次的
例：
She has a teenage daughter from a previous marriage.
她有个出自前一次婚姻的十几岁的女儿。
2.ADJ You refer to the period of time or the thing immediately before the one that you are talking about as the previous one. 前一个的
例：
It was a surprisingly dry day after the rain of the previous week.
这是继前一周的降雨之后出奇干燥的一天。

before /bɪˈfɔː/ CET4 TEM4
1.PREP If something happens before a particular date, time, or event, it happens earlier than that date, time, or event. 在 (某日、某时、某事件) 以前
例：
Annie was born a few weeks before Christmas.
安妮在圣诞节前几个礼拜出生。
Before World War II, women were not recruited as intelligence officers.
二战前，女性不被征募为情报官。
2.CONJ Before is also a conjunction. 在 (某日、某时、某事件) 以前
例：
Stock prices have climbed close to the peak they'd registered before the stock market crashed in 1987.
股票价格已经快爬升到了1987年股市崩溃前的最高纪录。
3.PREP If you do one thing before doing something else, you do it earlier than the other thing. 在 (做某事) 之前
例：
He spent his early life in Sri Lanka before moving to Canada.
移居加拿大前，他早年生活在斯里兰卡。
4.CONJ Before is also a conjunction. 在 (做某事) 之前
例：
He took a cold shower and then towelled off before he put on fresh clothes.
他穿上干净衣服之前，冲了个冷水澡，再擦干身子。
5.ADV You use before when you are talking about time. For example, if something happened the day before a particular date or event, it happened during the previous day. (某时、某事) 以前
例：
The war had ended only a month or so before.
战争大约在一个月前才结束。
6.PREP Before is also a preposition. (某时、某事) 以前
例：
It's interesting that he sent me the book twenty days before the deadline for my book.
有趣的是，在距离我书的截止日期20天前他把那本书寄给了我。
7.CONJ Before is also a conjunction. (某时、某事) 以前
例：
Kelman had a book published in the U.S. more than a decade before a British publisher would touch him.
科尔曼在美国已经出版了一本书，十多年后英国的出版商才愿意出版他的作品。

before可以单独作时间状语，是介词连词副词，而previous一般只用作形容词
满意请采纳，谢谢

before 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.