in later after ago before 的区分怎么用举些例子,说明各自表示什么时态before 2 days 还是before 2 days 两者一样还是不同的

这样说吧,in与将来一段时间连用,如i will come back in 2 days,later的用途比较广泛可用于多种时态{具体见后文},after跟一段时间用于过去时,点时间用于将来时和现在时
具体内容
later、after、ago、before的用法：
①“一段时间+later/ago”分别表示“(多久)以后/以前”,主要用于过去时态.
②“after/before+某个时刻”分别表示“在某时刻之后/之前”,此时两个词是介词.
③ago与before：ago只能用于过去时,before用于完成时.
如：He had an accident a weekago.(一周前出了一个事故).
Some yearslater,the boy became a very famous
singer.(数年后这个男孩成了著名的歌唱家).
Have you been therebefore?(你从前到过那儿吗?).
Aftera few years he gave up
smoking.(过了几年他戒了烟.)
I.after,in用法辨析
在表示以现在为起点的“在.之后”含义时,in之后应接时间段,after之后应接时间点,当以某个过去时间为起点时,after之后既可接时间点,也可接时间段.
如：It's three o' clock.I'll be back in an hour.
现在是三点,我一小时后回来.
The manager will come back after seven o' clock.
经理七点后回来.
Just after five the rain began to fall.
刚过五点就下起雨来了.
After three days I went to a party.
三天后,我去参加一个聚会.
II.ago,before用法辨析
ago表示以现在算起的“.以前”,与之连用的谓语动词用一般过去时,before则表示以从某个过去时间点算起的“.以前”,与之连用的谓语动词用过去完成时.
如：He lived in Beijing ten years ago.
十年前他住在北京.
He said that he had seen her two days before.
他说他两天前见过她.
in表示的时间1.“in+一段时间”意为“将来一段时间之内/后”.例如:I will return the book in four
days.我会在四天之内归还这本书的.I'll come and see you again in five
days.过五天我再来看你.2.也可用来表示“过去一段时间之内”.例如:The work was done in a week.这工作一星期内就做完了.
after表示的时间1.after作为介词,用来表示在某一时间或某一具体事件以后,与之连用的谓语动词可用过去时,也可用将来时.例如:I went to bed
after ten o'clock last night.我昨晚十点钟后上床睡觉.They will play football after three
o'clock in the afternoon.他们下午三点以后踢足球.2.after用作从属连词时,意为“在……以后”,引导时间状语从句.例如:I am
going to see my friends after school is over