in:
(1) prep. 在…里；在…中
word that shows where or what place
[例句]
There is no cloud in the sky.
晴空万里无云。
Glasgow is in Scotland.
格拉斯哥在苏格兰。
(2) prep. 进；入
word that shows where to
[例句]
Ray put his hand in the water.
雷把手放进水中。
(3) prep. 在；于（时间）
word that shows when
[例句]
Margaret started school in 1973.
玛格丽特一九七三年开始上学。
No,it was in 1970,not 1969.
不对，是在1970年，不是1969年。
(4) prep. 在…（时间）以内
word that shows how long
[例句]
I'll be ready in an hour.
我一小时以内准备好。
(5) prep. 在…（情况）中
word that shows how someone is
[例句]
My mother is in good health
我的母亲身体很好。
Emma was in tears.
埃玛哭了。
(6) prep. 穿；戴
word that shows what sort of clothes
[例句]
The policeman is in uniform.
警察穿着制服。
She dresses him in his new clothes.
她给他穿新衣服。
(7) prep. 在…（环境）下
word that tells about what is happening around us
[例句]
We walked in the rain.
我们冒雨行走。
They slept in the shade.
他们睡在树荫下。
(8) prep. 以…（方式），用…（语言）
word that shows what way,what language,etc.
[例句]
He spoke in Italian.
他讲话用意大利语。
They talked in English.
他们用英语交谈。
Please write in pencil,not in ink.
请用铅笔写，不要用钢笔写。
The letter was written in French.
信是用法文写的。
(9) prep. 从事（职业）；参加（活动）
word that shows where someone belongs
[例句]
He's in the army.
他在军队里
(10) adv. 向内；进入
word that shows where someone or something is going
[例句]
He just looked in for a moment.
他只是（在门外）往里头看了看。
Come in.
进来。
Step in,please.
请进来。
(11) adv. 在内；在家；在办公室
word that shows where someone or something is
[例句]
Is your brother in or has he gone to the match?
你弟弟是在家还是看球赛去了？
"Is Mr. Smith in?" "No,he's gone out for lunch!"
“史密斯先生在家吗？”“不在，他出去吃午饭去了。”
(12) adv. 时髦；流行
popular;liked by most people
[例句]
This year,short skirts are in.
今年时兴短裙。
(13) adv. （车，船）到达
arrived
[例句]
The train is in.
列车到站了。
我们所学的常用介词数量不多，因此我想在近段时间和kitty能给大家提供一些有用的东西。同时更希望同学们能在这里找到自己需要的东西。
：）
介词in和after的用法及区别
1)“in +一段时间”作“在……(时间)之后(内)”讲，常用于将来时或以一般现在时表示将来的句子中。例如：
①We'll finish it in two weeks. 半月后，我们将做完这项工作。
②Will you arrive there in a month?
你要在一个月之内到达那儿吗？
2)在过去时态的句子中，要表示“在……(时间)之后”则用“after +一段时间”或“一段时间+ after / later”。例如：
①After two days they arrived at a small village.
两天之后，他们到达一个小村庄。
②He left on Monday and returned after two days/two days after (or later).
他星期一走的，两天之后回来。
3)如“after +一时间点”可用于过去时或将来时，但不能用于现在完成时。
如：
①They will come back after three o'clock. 他们三点之后回来。
②I finished the work after ten last night. 昨晚十点钟之后我才做完工作。