表示原由：
1. for 表示原因,常与 sorry, famous, punish, praise, thank, blame等词连用.如：
I am sorry for what I said to you. 我后悔不该对你讲那些话.
2. at 指情感变化的原因,意为 “ 因听到或看到而 ……”.如：
He was surprised at the news. 听到这消息他大吃一惊.
3. from 指 “ 外在的原因 ”,如受伤、车祸等.如：
He died from the wound. 他因受伤而致死.
4. of 指 “ 内在的原因 ”,如病、饿等.如：
The old man died of hunger. 老人死于饥饿.
5. with指生理上或情感上的由外界到内心的原因.如：
Hearing the news, he jumped with joy. 他们听到这个消息,欣喜若狂.
He was shaking with anger. 他气得浑身发抖.
6. by表示外部的,尤其是暴力的或无意中造成某种结果的原因.
Her body was bent by age. 他因年老背弯了.
She took your umbrella by mistake. 我因弄错拿了你的雨伞.
7. because of/because 表示引起结果的直接原因.如：
He retired last month because of illness/because he ill.
8. owing to多表示引起某不良后果的原因.如：
Owing to the rain they could not come. 由于下雨他们没来.
9. thanks to表示引起某种幸运结果的原因,常译为“幸亏……,多亏……”.如：
Thanks to John, we won the game. 多亏约翰,我们才赢了这场比赛.
10. out of表示动机的起因,常译为“出于……”.如：
He asked the question out of curiosity. 他出于好奇才问了那个问题.
11. through多表示因局部而影响全局的原因.如：
The war was lost through bad organization. 战争因组织不周而失败了.
表示途径：
一、by表示用（方法、手段、途径等）或意为乘坐（交通工具）,后接的名词前面通常不用冠词.
Mr.Green usually goes to work by bus.
He makes a living by selling newspaper.
二、in表示用（方式、材料、途径、语言）
He wrote many letters in English.
You can do this in a different way.
三、with表示带着、伴随,后接具体的工具,手段、材料或其他行为方式.
He plays table tennis with his left hand.
He told me to write with a pen.
四、through表示以（方法、手段）、经由
We learn a second language through listening, speaking, reading and writing.
I got to know him through a friend.