By是个很常见的介词，今天我们来介绍它的几个常见用法：

1、被；由
The feast was served by his mother and sisters. 这顿美餐是他母亲和他的姐妹们准备的。
The child was saved by a PLA man. 这孩子是由一位解放军战士救活的。
He was praised by the teacher. 他受到了老师的表扬。

2、表明作者，“（图书、音乐、绘画等）由……创作，出自”。
a painting by Van Gogh... 一幅凡•高的画
This book is written by Jack. 这本书是杰克写的。
a collection of piano pieces by Mozart （莫扎特钢琴曲集）

3、表示方式、方法、手段等，“通过；用；凭”。
We'll be travelling by car. 我们将开车旅行。
They can read by touch. 他们可以通过手摸来阅读。
I send a letter by post. 我通过邮局寄信。
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。

4、在…旁边；接近
Judith was sitting in a rocking-chair by the window. 朱迪丝正坐在窗户边的一张摇椅里。
He gave me a story book when nobody was by. 当附近无人的时候他把小说给了我。

5、经过；经由
He kept walking and passed by me on his side of the street. 他一直在街对面走着，并与街这边的我交错而过。
He hurried by without a word. 他匆匆地走过去没有说一句话。
Time has gone by. 时间已过去了。

6、在…时候；到…之前；不迟于
By eight o'clock he had arrived at my hotel. 到8点时，他已经到达我住的宾馆了。
We all knew by then that the affair was practically over. 到那时，我们都知道事情实际上已经结束了。
We should finish our work by tonight. 今晚之前我们要结束工作。

7、（乘或除）以
230cm divided by 22cm is 10.45cm. 230厘米除以22厘米等于10.45厘米。

8、表示幅度
Violent crime has increased by 10 percent since last year. 自去年以来增加了10%。
The shot missed her by miles. 那一枪没打中她，差了十万八千里。

9、以…计；按…计
Parcels arrived by the dozen from America. 包裹成打地从美国运来。
billing is by the minute. 以分钟计账。

By的用法很多，但其实很多意思可以合并起来记忆，希望大家能够好好掌握。