in after later before ago earlier until 状语 区别

时间状语小结- 前前后后
In
【in + 时间段】介词，后接时间段，不能与时间点连用。

In用来表示从现在算起的“过一段时间以后”，常用在将来时的肯定句里，一般与go, come, start, arrive, return (be back), finish等表示瞬间动作动词连用，通常用于将来时或含有将来意义的句子。

They will arrive in half an hour. 半小时后他们将到达。

He will leave in a minute. 他一会儿就走。

After介词其后既可接时间点，又可接时间段。

【after+时间段】表示以过去时间为起点的一段时间以后，因此通常与过去时连用；
He left there after two o'clock that afternoon．那天下午两点以后，他离开了那儿。

He started to go again after two days．两天以后，他又走了。

【after+时间点】如果用于一般将来时，那么其后应接时间点。

He'll come here after three o'clock．他3点钟后将来这儿。

He will arrive after five o’clock. 他5 点钟以后到。

【after+句子】连词，其后可接从句，连接2个句子。

I'll call you after I've spoken to them. 我和他们谈了以后就给你打电话。

After she had mixed flour with water, the children came home. 她用水和好面之后，孩子们回来了。

【after 单独使用】副词later in time; afterwards 表示以后
And they all lived happily ever after . 从此以后他们都过着幸福的生活。

Later副词, 常常放在时间段的名词之后。

可以指过去，也可指将来。

【时间段+later】
Three days later he got to Beijing．＝After three days he got to Beijing．他三天以后到达了北京。

At first she was asleep. Half an hour later=After half an hour, she woke up. 开始她睡着了，半小时后醒来了。

【Later单独使用】
The radio says that the sun will come out later. 收音机里说太阳稍后会出来。

ago【时间段+ago】副词，用于一般过去，它所指的时间是从现在算起, 即现在的过去，因此通常与一般过去时连用;
Tom's grandpa came to live with him two years ago. Tom 的爷爷两年前来和他住在了一起。

（但since ... ago，照样要用完成时，因为since 表示“自从...以来”He has lived in Beijing since 10 years ago.）
It was stolen twenty years ago when Ted was a boy of fifteen. 那辆自行车是在20年前当泰德还是个15岁的小伙子时被偷去的。

Before
【时间段+ before ：ten years before】
副词，用于完成时(过去完成时), 它所指的时间不是从现在算起，而是从过去某一时刻算起，即指过去的过去，因此通常与过去完成时连用(尤其用于宾语从句中)。

His parents died ten years ago．他父母十年前都去世了.
He said that his parents had died ten years before．他说他父母亲十年前都去世了.
有时before=earlier
A few hours earlier, someone had told the police that thieves would try to steal the diomands.
几小时之前，有人已告诉警察说，小偷打算盗窃那些钻石。

）
【before + 时间点before ten o’clock】介词，表示在某一点时间或事件以前时, 只用before不用ago,这种用法是将before当作介词或连词使用
They will come back before six o’clock．
It is hoped that this will be finished before the year 1995
【before + 句子】Before可作连词，连接从句
Do it before you forget. 尽早动手，免得忘了。

Did she leave a message before she went? 她走之前留言了吗？
【before副词，单独使用】(即不连用具体时间)，泛指一般意义的“以前”，只用before不用ago,此时可用于一般过去时，也可用于现在完成时。

Have you seen this film before?
He asked me whether I had been to the Great Wall before．
Before 小问题?
Before long = soon不久以后，相当于副词，用于一般将来时和一般过去时
I hope you will be back before long.
Long before = long time ago 很久以前，常用于过去完成时和现在完成时
I saw that film long before.
long before ，before可以为连词，因此可以引导时间状语从句。

后面可以跟一个句子，这时候before 是连词，引出一句时间状语，表示“在...... 前很久”的意思。

如：He had been a party member long before he came to our school. 他到我们学校来之前早就是一个党员了。

Earlier
【时间段+ earlier】early 形容词的比较级，作定语(修饰省略掉的后半句)
He finished his homework 30 minutes before/earlier. 此处before和earlier可以互换。

He told us to be here at 9 a.m. but we arrived 20 minutes earlier. 此处earlier是形容词词性，作定语，修饰省略掉的后半句than what he had told us，因此不可用before替换。

【Earlier 副词，单独使用】
Earlier 有比较之意
I should have come earlier 我本该早点来的
I should have come before 我本该以前来的
Earlier 相比before时间比较短
I met him earlier 我刚刚才碰到他
I met him before 我以前碰到过他
He came before me. 此处before为连词，不可用earlier。

如果用earlier，应该为He came earlier than I did. Until Before表示“在…之前”，而until表示“直到…才…”。

两者有可以互换的情况，也有不可互换的情况。

相同方面：
如果主句（或简单句）中的谓语动词为延续性动词的肯定式: stand, stay, talk, wait, be，用until或before均可，但在意义上有一定的差别。

如：
She lived in the house until he came back. 她在那所房子里一直住到他回来。

（强调“到此为止”）
She lived in the house before he came back. 在他回来之前，她一直住在那所房子里。

（强调“在……之前”）
如果主句（或简单句）中的谓语动词为非延续性动词的否定式：open, start, leave, arrive, finish, stop，用until或before 均可，且意义上没有差别。

如：
The moon will not come out until / before the clouds disappear. 云散了月亮才会出现。

Until 小结
主句是肯定句则表示主句动作的终止时间；......until
主句是否定句则强调主句动作的起始时间：not......until
不同方面：
如果主句（或简单句）中的谓语动词为非延续性动词的肯定式，只能用before，不可用until。

如：
He can come here before sunset. 在日落之前他能来这。

如果主句（或简单句）中的谓语动词为延续性动词的否定式，多用before，一般不用until。

如：
He has not done anything before she comes. 在她来之前，他什么也没做。

在It wasn't until ... that 强调结构中不用before。

如：
It wasn't until this morning that I heard the news. 直到今天早上我才听到这个消息。

By表达“不晚于某时”，也可以翻译为“截止到”。

指某动作将在某一时刻或该时刻之前完成。

【by+时间点：by the time/by the end of last month】
By the 1920s, he had become an explorer, searching for the tombs of the Egyptian kings.
到20世纪20年代的时候他已经成为寻找古埃及王墓方面的探险家。

How many English books had you read by the end of last year?到去年年底以前你看过多少本英文书?
Can you finish the work by five o'clock?你五点钟前能完成工作吗？
I'll have it done by tomorrow.我将于明天之前让人做完这件事。

By this time next week we'll be in New York.下星期的这个时候我们将在纽约。

He ought to have arrived by now/by this time .他现在应该已经到了。

Since 表“从.....开始”有延续含意
【since+时间点】，表达从那个点开始，延续到现在，所以翻译为“自从（过去某个时间）以来”，既然跨度为两个时间，自然要用完成时。

They have been friends since childhood. 他们从幼时起一直是好朋友。

She's been skiing since childhood. 她从幼时起就开始滑雪。

It's been an age since we met. 我们好久未见面了。

For 也有延续含意
【for+时间段】表示“延续….之久”，其中：
与现在完成时连用，表达从过去延续到现在结束；
与过去时连用，表达过去一段已经终结的时间；
与将来时连用，表示延续到将来的一段时间。

Some even have been planting this dream in their mind for years.
有些人甚至多年来一直在他们的脑海中有这样的憧憬。

（完成时）
I organized an English club and was the captain of the club for a year.
我组织过一个英语俱乐部，并担任了一年的队长。

（和过去时）
They will stay in China for two years.
他们将在中国待上两年。

（和将来时）。