平时谁都知道in是一个介词，没有想到它还能作形容词、副词和名词；请看：
in
[ɪn]
prep.
采用（某种方式）;穿着，带着;（表示位置）在…里面，（表示领域，范围）在…以内;（表示品质、能力等）在…之中
adv.
在家;进入，到达;流行;当选
adj.
在内的，朝内的;在位的，执政的;[口语]流行的，时髦的;（车等）到站的
n.
执政党，掌权者;知情者;<美口>入口，门路;<体>（板球或棒球）攻球的一方
复数： ins
一、介词
在（某范围或空间内的）某一点
a country in Africa
非洲的一个国家
The kids were playing in the street.
孩子们在街上玩。
It's in that drawer.
它放在那个抽屉里。
I read about it in the paper.
我是在报纸上读到这事的。
2
在（某物的形体或范围）中；在…内；在…中
I couldn't bear to see my reflection in the mirror
我不忍看镜子里自己的样子。
She was lying in bed.
她躺在床上。
sitting in an armchair
坐在扶手椅里
Leave the key in the lock.
把钥匙留在锁孔里。
Soak it in cold water.
把这东西浸泡在冷水里。
3
进入
He dipped his brush in the paint.
他把毛刷在涂料里蘸了蘸。
She got in her car and drove off.
她钻进汽车里，开走了。
4
构成…的整体（或部分）；包含在…之内
There are 31 days in May.
五月份有31天。
all the paintings in the collection
收藏品中的所有画作
I recognize his father in him (= his character is similar to his father's) .
我在他身上看到了他父亲的气质。
5
在（某段时间）内
in 2005
在2005年
in the 18th century
在18世纪
in spring/summer/autumn/winter
在春 / 夏 / 秋 / 冬天
in the fall
在秋天
in March
在三月
in the morning/afternoon/evening
在上午 / 下午 / 晚上
I'm getting forgetful in my old age.
我上了年纪，变得健忘了。
6
在（某段时间）之后
It will be ready in a week's time (= one week from now) .
只需一周的时间就会准备好。
She learnt to drive in three weeks (= after three weeks she could drive) .
她花三个星期就学会了开车。
7
(used in negative sentences or after first , last , etc. 用于否定句或first、last等之后) 在（某段时间）内
for a particular period of time
I haven't seen him in years.
我有好些年没见过他了。
It's the first letter I've had in ten days.
这是我十天来收到的第一封信。
8
穿着；戴着
dressed in their best clothes
穿着他们最好的衣服
the man in the hat
戴帽子的男子
to be in uniform
穿着制服
She was all in black.
她穿着一身黑。
9
（用以描述具体的环境）
We went out in the rain.
我们冒雨出去了。
He was sitting alone in the darkness.
他独自坐在黑暗中。
10
（表示状态或状况）
I'm in love!
我恋爱了！
The house is in good repair.
这所房子保养得不错。
I must put my affairs in order.
我必须整理整理我的事务。
a man in his thirties
一位三十多岁的男子
The daffodils were in full bloom.
水仙花盛开了。
11
参与；参加
involved in sth; taking part in sth
to act in a play
参加演戏
12
（显示工作或职业）
used to show sb's job or profession
He is in the army.
他在军队服役。
She's in computers.
她从事计算机业。
in business
从商
13
（显示某物的形式、形状、安排或数量）
used to show the form, shape, arrangement or quantity of sth
a novel in three parts
分为三部的小说
Roll it up in a ball.
把它卷成一个球。
They sat in rows.
他们一排一排地坐着。
People flocked in their thousands to see her.
现场聚集了数以千计的人争相目睹她的风采。
14
（表示使用的语言、材料等）
Say it in English.
用英语说吧。
She wrote in pencil.
她用铅笔写的。
Put it in writing.
把它写下来。
I paid in cash.
我用现金支付的。
He spoke in a loud voice.
他大声说话。
15
关于；在…方面
She was not lacking in courage.
她并不缺乏勇气。
a country rich in minerals
矿藏丰富的国家
three metres in length
三米长
16
做…时；…发生时；当…时
In attempting to save the child from drowning, she nearly lost her own life.
她在抢救落水儿童时，自己差点丧命。
In all the commotion I forgot to tell him the news.
在一阵混乱之中我忘了告诉他那个消息。
17
（引出具某种品质的人的名字）
used to introduce the name of a person who has a particular quality
We're losing a first-rate editor in Jen.
我们即将失去珍这位一流的编辑。
18
（显示比率或相对数量）
Last year, one in five boys left school without a qualification
去年，五分之一的男孩没有获得资格证书就离校了。
a gradient of one in five
五分之一的坡度
a tax rate of 22 pence in the pound
每英镑22便士的税率
19. in that
原因是；因为
She was fortunate in that she had friends to help her.
她很幸运，有一些朋友帮助她。
I'm lucky in that I've got four sisters.
我很幸运，因为我有4个姐姐。
二、副词
1
在里面；在内
We were locked in.
我们被锁在里面了。
I can't drink coffee with milk in.
我不能喝加牛奶的咖啡。
2
进入
She opened the door and went in.
她打开门进去了。
The kids were playing by the river and one of them fell in.
孩子们在河边玩耍时，其中一个突然落水了。
3
在家里；在工作单位
Nobody was in when we called.
我们打电话时家里没人。
反义词： out
4
(of trains, buses, etc. 火车、公共汽车等) 在车站；在停靠站
The bus is due in (= it should arrive) at six.
公共汽车应该在六点钟到站。
5
(of letters, etc. 信件等) 收到；被投递到
received
Applications must be in by April 30.
申请务必于四月三十日之前寄到。
6
(of the tide 潮汐) 上涨；在最高点
Is the tide coming in or going out?
现在是涨潮还是落潮？
7
当选
Several new councillors got in at the last election.
几位新政务委员在最近一轮选举中当选。
8. be in at sth
…发生时在场
My flatmate was in at the time
我的舍友当时在房间里。
They were in at the start.
开始时他们在场。
9. be in for sth
即将经历，即将遭受（不愉快的事）
He's in for a shock!
他很快就会感到震惊的！
I'm afraid we're in for a storm.
看来我们就要遇到风暴了。
10. be/get in on sth
参与；了解
I'd like to be in on the plan.
我很想参与这项计划。
Is she in on the secret?
她知道这个秘密吗？
11. in and out (of sth)
时常出入
He was in and out of jail for most of his life.
他大半生的时间都是监狱的常客。
三、形容词
表示“流行的；时髦的 ”
Purple is the in colour this spring.
紫色是今年春天的流行色。
Exotic pets are the in thing right now.
奇异的宠物眼下很时髦。
Short skirts are in again.
现在又时兴穿短裙子了。
A few years ago jogging was the in thing...
几年前慢跑很流行。
四、名词
主要用法：
1.have an in with sb
对某人有影响
2. the ins and outs (of sth)
（尤指复杂或难的）全部细节，详情
the ins and outs of the problem
问题的来龙去脉
He quickly learned the ins and outs of the job.
他很快就掌握了工作的全部诀窍。
..the ins and outs of high finance...
大宗金融交易的详情
