1．by
（1）表示方法，手段。即“用。。。， 通过。。。。”相当于by means of 如：
All work had to be done by hand 所有的工作都是手工进行的。
He makes a living by teaching 他以教书为生。
（2）表示传达、传递的方式或煤介。如：
How did you send the letter, by airmail or by ordinary mail?
你是怎么发送的这信，是通过航天邮件还是普通邮件？
（3）表示用交通工具、通讯工具后接名词单数，不加冠词。如：
He came by train, but his wife came by bus. 他是乘火车来的，可是他老婆是坐公共汽车来的。
注意下面两句的区别：
Did you come by train? =Did you come in his car / on my bike?
“by +抽象名词”构成的词组有：by accident / by chance / by diligence / by effort / by force / by heart / by luck / by mistake / by hard work.
（4）指数量增加或减少到的程度，相差。
We lost the match by one goal 我们仅以一球之差输了比赛。
（5）根据，按照
pay sb by the hour /day/week
Sell sth by the pound /meter/ dozen
sell sth by weight/length
As a rule，domestic servants doing odd jobs are paid by the hour 通常，家政服务是按照小时计酬的。
2. through
（1） 表示“以；通过；经由”。如：
He succeeded through hard work.
（2） 空间上通过，透过，经过
Light comes in through the window。光线从窗户进来。
（3） 时间上通过， 自始至终，从头到尾经过
He often works through the night 他常常通宵工作。
注意：在表示手段时，by, through有时也可换用。如：
Through / By his efforts he succeeded in making so many useful inventions