介词by有五个常用意思和五个常用短语，现归纳如下。
1.by表示“在……旁边，靠近”。比如：Stand by me.站在我身边。The telephone is by the window.电话在窗户旁边。
2.by指时间时，意思为“……之前，不迟于”。比如：I shall be back by 6 o’clock.我最迟六点钟回来。
By next Monday we ought to have finished the homework.下星期五之前我们应该完成了作业。He ought to have arrived by now/by this time.他现在应该已经到了。
3.by表示“被”。比如：I was amazed by their lack of professionalism.我为他们的缺乏职业精神所震惊。We want to hear the symphony by Beethoven.我们想听贝多芬创作的交响曲。
4.by表示“以……方式”。比如：The house is heated by gas.这房子是煤气供暖的。I will contact you by letter.我会给你写信联系的。
If you're travelling by car, ask whether there are parking facilities nearby.如果你开汽车旅行，问问附近是否有停车设施。
5.by表示“根据，按照”。比如：Don’t judge a person simply by his appearance.不要简单地根据外表来判断一个人。By my watch it is two o'clock.我的表是两点钟。
由by构成的常见短语如下：
1.by and by指“不久，迟早”。比如：We'll surely meet again by and by.不久我们一定能再相见。By and by the days turned warm.渐渐地，天变暖了。He'll come round by and by.他会慢慢想通的。
2.by oneself指“独自地；独立地”。比如：The man is sitting by himself in a corner.这个男人正独自坐在角落里。I didn't know if I could raise a child by myself.我不知道是否能独立抚养一个孩子。
3.by chance指“偶然，碰巧，意外地”。比如：I saw the letter purely by chance.我看见这封信纯属偶然。Several years after they'd split up they met again by chance in Paris.他们分手几年以后在巴黎又偶然相遇。
4.by mistake的意思是“错误地，由疏忽所致，无意地”。比如：I did it by mistake.我误做了这事。I took your bag instead of mine by mistake.我不巧错拿了你的包。
5.by and large指“大体上，总的来说”。比如：By and large, I enjoyed my time at school.总的说来，我在学校很开心。By and large, these people are peace-loving citizens.这些人总的来说都是热爱和平的公民。
