before.
我们的孩子以前从未乘飞机旅行过。
It’s easier to get there by car.
开车去那里比较容易。
注意：by 与运输方法之间不能有如 a/an，the，some，my 或 his 等之类的其他限定词；当 by 与运输方法之间有其他限定词时，用介词 in 或 on，例如：
芭芭拉正在安的车里旅行。
Barbara is travelling in Ann’s car. (正确)
Barbara is travelling by Ann’s car. (错误)
你坐过小飞机吗？
Have you ever travelled in a small plane? (正确)
Have you ever travelled by a small plane? (错误)
2. 当表示靠步行到达某个地方时，用 on foot，而不用 by foot，例如：
I used to go to work on foot.
我往常都是步行去上班。
He vainly hope to travel round the world on foot.
他梦想步行周游世界。
三、by 通信方法
By 通信方法，表示如何与他人交流，常见的通信方法有 telephone，fax，mail 和 post 等，例如：
I'll send the original to you by post.
我将把原件邮寄给你。
They usually exchanged messages by telephone.
他们一般通过电话互通消息。
Please confirm the order by email.
请用电子邮件确认订单。
四、by 付款方式
By 付款方式，表示如何付款，常见的通信方法有 credit card 和 cheque 等，例如：
It is very convenient to pay by credit card.
用信用卡付款非常方便。
I have no cash with me, may I pay by cheque?
我没有带现金，可以付支票吗？
注意：用现金支付时，不能用 by cash，而用 in cash，而且在口语中，in 有时可以省略，例如：
假如你支付现金的话，我会不胜感激。
I would appreciate it if you paid by cash. (错误)
I would appreciate it if you paid in cash. (正确)
David paid cash for the newspaper.
大卫用现金买了报纸。
五、by 与被动语态
在被动语态中，by 表示谁执行了动作，例如：
大卫正在打扫厨房。
David is cleaning the kitchen. (主动)
The kitchen is being cleaned by David. (被动)
我被那响声吓坏了。
The noise frightened me. (主动)
I was frightened by the noise. (被动)
我们学校组织了音乐会。
Our school organised the concert. (主动)
The concert was organised by our school. (被动)
六、by 反身代词
By 反身代词，表示单独做某事，总共有8个反身代词 myself，yourself，himself，herself，itself，ourselves，yourselves 和 themselves，有时用 all 来表示强调，例如：
Let's do something by ourselves.
让我们自己做点什么吧。
My parents often go on holiday by themselves.
我父母经常一个人去度假。
Did you build that castle all by yourself?
那城堡是你自己建的吗？
I was all by myself in the house last night but I didn’t mind.
昨晚我一个人在屋里，但我不介意。
七、by V-ing
By V-ing，描述了如何做某事，它提供了更多关于如何实现特定结果的信息，例如：
You can turn on the radio by pressing that button.
按那个按钮你可以打开收音机。
Make the sauce by boiling the cream and stock together in a pan.
把奶油和高汤一起放在平底锅里熬煮来制作调味料。
八、by 时间表达式
By 时间表达式，用来暗示不迟于某个时间做完某事，也就是这个时间点是做完某事的最后时间，通常后面接确定的时间，如几点或星期几等，意为”不迟于“，例如：
Guests must vacate their hotel rooms by 11 am.
客人必须在上午11点前离开酒店房间。
Please send us the payment by tomorrow.
请在明天之前把货款寄给我们。
They said that the plumber would be here by Monday.
他们说水管工星期一会到。
The postman is always here by 11 am.
邮递员总是在上午11点以前到这儿。
注意：此时的 by 与 before 的在时间上是有很大差别的，例如：
a. She has to submit her homework before Friday.
b. She has to submit her homework by Friday.
解析：句a的内在意思是作业最迟必须在星期四交上来，而句b的内在意思是作业必须在星期五午夜前交，两句差了12个小时，所以它们表示的截止时间还是有差距的，要认真使用，特别是在上级交代下属任务的时候。
九、by 数量或度量
By 数量或度量，用来讨论度量和数量的增减，例如：
The price of fuel has increased by 12% this year.
今年燃料价格上涨了12%。
The room measures fifteen feet by twenty feet.
房间15英尺宽20英尺长。
It was getting worse by the minute .
情况急速恶化。
当用于表示购买、出售或测量某物的时间或数量时，by 后面常跟如 day，hour 或 metre 等基本计量单位，此时在 by 和计量单位之间加定冠词 the，且经常跟 pay 或 sell 连用，意为“按…计算（出售）”等，例如：
They're paid by the hour.
他们的报酬是按小时计算的。
We only sell it by the metre.
我们只按米出售。
十、by 人体部位或物的部分
By 人体部位或物的部分，表示触及或抓住的人或物的部分，例如：
He took Dickon by the hand to lead him into the house.
他牵着迪康的手把他领进屋。
She seized her by the hair.
她揪住她的头发。
Pick it up by the handle!
抓着手柄把它提起来！
十一、by 用来补充有关出生地、职业等的信息
用于提供更多关于某人来自何处、某人做什么等的信息，例如：
Her parents were in fact American by birth.
她的父母在血统上其实是美国人。
He was an electrician by profession.
他的职业是电工。
十二、by 特殊的名词
By 特殊的名词，表示原因，常见的特殊的名词有 chance，mistake 和 misadventure，意为“由于”，例如：
I saw the letter purely by chance.
我看见这封信纯属偶然。
He has been arrested by mistake.
警方误抓了他。
十三、by 表示经过
By 表示经过，相当于 pass，例如：
He walked by me without speaking.
他一言不发地从我身边走过。
Three people walked by the house as Henry opened the door.
亨利开门时，三个人从房子旁边走过。
此时的 by 也常用作副词，例如：
He hurried by without speaking to me.
他没和我说话就匆匆过去了。
Time goes by so quickly.
时光飞逝。
十四、by 意为“从…看，依，按照”
此时相当于 according to，例如：
By law, you are a child until you are 18.
按照法律规定，18岁之前是未成年人。
By my watch it is two o'clock.
我的表是两点钟。
十五、by 用于乘除运算
5 multiplied by 3 equals 15.
5乘以3等于15。
15 divided by 3 equals 5.
15除以3等于5。
十六、by 表示短暂拜访
此时 by 是副词，例如：
You just go on ahead. I'll come by later.
你只管先往前走。我随后就来。
Drop by sometime.
有空儿来坐坐。
关注外语行天下，后期会更精彩。
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