作为一个以英语为母语的人，你可能会意识到in,on与at之间存在差异。而大多数学生则掷骰子决定该用哪一个。好吧，收起你的骰子，让我们来学习这三个单词之间的区别。

我认为想一想这些介词的定义是很有帮助的。只是作为一个提示，介词是用来辨别句中位置关系的语体。因此，如果你在谈论一个对象或一个人，并且你想包括一个地方，那么介词可以帮助你来表述。

IN
在...里面

So first, let us look at the word in. This word means surrounded by or encircled by. If you want to say something is encased or surrounded by anything, this is your go to preposition.
首先，让我们看看in这个单词。这个词的意思是被包围或被围绕。如果你想说某物被什么东西包围或围绕，这就是你要找的介词。

Right now, I am in my room.
现在，我在房间里。

There are four walls, a ceiling and a floor. I am surrounded by the room.
这儿有四堵墙，一个天花板和一个地板。我被整个房间包围。

This also works for cities and countries. Go ahead look outside. What country are you surrounded by? Then you are in this country!
这也适用于城市和国家。往前看外面。你周围是哪个国家？那么你就在这个国家！

I am in the United States of America. I am in New York City.
我在美利坚合众国。我在纽约。

What about water? Yes, that too.
水呢？是的，也一样。

She is in the pool. She is in the ocean. He is in the lake or pond or bathtub.
她在游泳池里。她在海里。他在湖里、池塘或浴缸里。

Again, if you are surrounded by the location, then you are in that location.
同样，如果你被某一地点所包围，那么你就处在那个位置上。

If you say that you are in a door (I hope that you are not), then as a fluent English speaker, I understand that you have broken the door and you are somehow trapped in the door.
如果你说你在一个门里（我希望你没这么说过），然后作为一个流利的说英语的人，我知道你打破了门，你不知怎么被困在门上。

Here are some more examples:
下面是一些例子：

I am in bed. (The covers are over me or I am under a blanket).
我在床上。（被子盖在我身上，或者我在毯子下面）。

You can find the answer in the book. (The answer is surrounded by the book, this is easier to imagine if the book is closed).
你可以在书中找到答案。（答案在书里，如果这本书合起来就更容易想象了）。

He looks so cute in the picture. (The outline or frame of the photo is surrounding him).
他在照片里看起来很可爱。（照片的轮廓或框架围绕着他）。

Betty is in school. (This means that she is a student and not physically at the school).
贝蒂在上学。（这意味着她是学生而不是单纯地在学校里）。

ON
在...上面

Now let’s talk about on as a preposition. For me, the word on means specific location. I am not talking about being surrounded by something. I am focusing on a more specific location.
现在我们来谈谈介词on。对我来说，on是指特定的位置。我不是说被什么东西包围着。我把重点放在一个更具体的位置上。

For example
例如

I am in my room, but I am on a chair.
我在房间里，但我坐在椅子上。

I have given you a more specific location to help you locate me.
我给了你一个更具体的位置来帮助你找到我。

Perhaps, you need to find keys that belong to someone. You ask them in English, Where are your keys? They will answer, The keys are on the table.
也许，你需要找到属于某人的钥匙。你用英语问他们，你的钥匙在哪里？他们会回答的，钥匙在桌子上。

If they were to answer you like this, The keys are in the living room. It might take you a little longer to find those keys, since it wasn’t so specific.
如果他们像这样回答你：钥匙就在客厅里。你可能要花更长的时间才能找到那些钥匙，因为回答不是那么的具体。

Here are some more examples:
下面是一些例子：

I am on the bed. (I am NOT under the covers or blankets).
我在床上。（我不在被子或毯子下面）。

Her office is on the third floor. (A specific location in the building).
她的办公室在三层。（建筑物中的特定位置）。

I often hear my students tell me, My workbook is on my house. In English, this means that they have thrown their workbook on top of their house, on the roof. Why did they do that?
我经常听到我的学生告诉我，我的工作手册在我的房子上。在英语中，这意味着他们把他们的练习本扔在房顶上。他们为什么要那样做？

Well, thankfully they did not throw it on their house. They meant to say, My workbook is at my house.
谢天谢地，他们没有把钱丢在房顶上。他们的意思是说，我的工作手册在我家里。

AT
在...

This brings me to the next preposition at. At means general location. If the place that you are talking about is big, like an airport, hotel or even your house (with many rooms and locations) then you should use at.
这就引出了下一个介词at。它指的是大体的位置。如果你所谈论的地方很大，比如机场，旅馆，甚至你的房子（有许多房间和地点），那么你应该使用at。

This lets the listener know your general location.
这能让听众知道你的大体位置。

For example
例如

My wife calls and says, Where are you?.
我妻子打电话说，你在哪里？

I would answer, I am at home. (Or even I am home)
我会回答，我在家里。（甚至“我在家”这样回答也可以）

If she wanted to know more specifically, (for example, she is home and she can’t find me) she would say, Yes, but where in the house?
如果她想更具体地知道，比如说，她在家，却找不到我，她会说问：是的，但是在家里的哪块儿呢？

I would respond, I am in the kitchen.. The preposition in lets her know that I am surrounded by the kitchen and if she wants to find me, then she can go there.
我会回答：我在厨房里。介词in让她知道我在厨房里，如果她想找我，她就可以去那里。

We can use at for the following situations:
我们可以在下列情况下使用at：

They are at the beach. (This is a big location).
他们在海滩上。（这是个大地方）。

They are at the airport.
他们在机场。

I am at the hotel or conference.
我在旅馆或在开会。

Sara is at work. (This lets me know her general location).
萨拉在上班。（这让我知道她的大体位置）。

Someone is at the door. (There are many different places someone can stand while next to a door. Just move 1 cm and you are at a “new” location.
有人在门口。（在门旁边有许多不同的地方可以站着。）只要移动1厘米，你就站在一个“新”的位置。

Bob is at school. (You can go to this school and you will find Bob there).
鲍伯在上学。（你可以去这所学校，你会发现鲍伯在那里）。

Now, at can also be used for time. I argue that the position of the earth and the sun are at a general location (given the huge size of the two objects). This is just my way of simplifying the way to remember when to use the preposition at.
现在告诉你，AT也可以用在时间前。我认为地球和太阳同处于在一个大体的位置上（考虑到两个物体的巨大尺寸）。这正是我简化使用介词短语的方法。

You can still think of the definition for at as a general location for time.
你仍然可以把它定义为时间上的大体位置。

So, I have English class at 8am.
所以，我在8点上英语课。

BUT
但是

I have English class on Tuesday. (It is a specific day of the week).
我星期二有英语课。（这是指一周中的特定一天）。

I love to relax on the weekend. (It is a specific part of the week).
我喜欢在周末放松一下。（这是指本周的一部分）。

My birthday is on December 7th. (This is a specific day in December).
我的生日是12月7日。（这是十二月中的某一天）。

My birthday is in December. (My birthday is on the 7th, but it is surrounded by the other days in the month.
我的生日在十二月。（我的生日在十二月份的第七天，但这一天被这个月的其他日子包围着。

I was living in France in 2007. (The entire year of 2007 was surrounding the time that I lived in France).
我2007年住在法国。（整整2007年都是我在法国的时候）。

I have breakfast in the morning. (Morning starts from about 6am until 11:59.).
我早上吃早饭。（早上是指从早上6点到11:59一段时间）。

So we use the preposition “in” because this is a time that is surrounding you during that time period.
所以我们使用介词“in”，因为这是一个伴随着你的时间段。

The same goes for afternoon and evening.
下午和晚上也一样。

Night is different because the darkness is changing (you know with daylight savings time and such). So you say “at” when using night.
黑夜是不同的，因为黑暗在变化的（你知道白天节约时间等）。所以你用晚上说“在”。

Please, be careful when driving at night.
晚上开车时要小心。

There are some other things to keep in mind when talking about time.
谈论时间还有一些其他的事情要记住。

Let us say that you want to plan a brunch Monday morning. Because we have the specific day of the week “Monday”, we give preference to that word and the preposition is on.
我们打个比方说，你在星期一早上计划吃早午餐。因为我们有一周中特定的一天“星期一”，我们偏爱那个词，所以用介词on。

I will have brunch on Monday morning.
我星期一上午吃早午餐。

Here are some more examples:
下面是一些例子：

She went dancing on Saturday night.
她星期六晚上去跳舞了。

They went to a restaurant on Friday evening.
星期五晚上他们去了一家餐馆。

When talking about future time (you know what you plan to do later), be sure to use the preposition in.
当谈论将来的时间（你知道你以后打算做什么）时，一定要使用介词in。

For example
例如

I will see you in two weeks.
我两周后见你。

She will graduate in 4 years.
她将在4年内毕业。

When talking about TRANSPORTATION, the two prepositions on and in follow different rules. Don’t worry, they are pretty simple.
当谈到交通时，两个介词on和in都遵循不同的规则。别担心，它们很简单。

ON: When you CAN WALK around on the transportation.
你可以在交通工具上到处走动。

The idea here is if the mode of transportation has enough room to walk around, then use on.
这里的意思是，如果交通工具上有足够的空间走动，就使用on。

For example:
例如：

I was on the plane when you called me. (There is enough room on a plane to walk around).
你打电话给我时我在飞机上。（飞机上有足够的空间走动）。

I was on the bus yesterday. (Again, there is sufficient room to be able to move around with your feet on a bus).
昨天我在公共汽车上。（同样，你有足够的空间在公共汽车上走动）。

IN: When you can NOT WALK around on the transportation.
使用in的情况：当你不能在交通工具上走来走去的时候。

If the vehicle too small to walk around, then you need to use in.
如果车辆太小你不能在上面走动，那么你需要使用in。

For example
例如

Get in the car. (There is not enough space in a car to walk around).
上车。（车里没有足够的空间走动）。

Please, be careful when you get in the taxi.
当你上出租车时要小心。

The opposite follows the same rule. The opposite of ON = OFF.
反义词则遵循相同的规则。上车的反义词=下车。

So you get off a bus.
所以你下了公共汽车。

The opposite of IN = OUT
进去的反义词＝出来

So you get out of a car.
所以你从车里出来。