for
1. prep.
(1)因为，由于 for this reason
(2) 表示时间\距离长度； for three days； He ran for three miles.
(3) 为了 ：What do you come here for?
(4) 表示等价交换： He sold his house for 30,000 dollars.
(5) 开往；前往 We set off for London.
(6) 代；替；代表 Red is for danger.
(7) 用于for + 名词或代词 + to + 不定式动词的名词短语中
The bell rang for the lesson to begin.
2. conj 因为 （表示推测或附加的原因， 前后为并列句）
It must have rained last night, for the ground is wet.
Kuntta ( a prisoner ) knew day broke, for he heard the birds singing.
尽管for 的用法较多，但记住常用的几个就可以了。
for的用法的确很多，可用作介词和连词，介词用法尤为丰富。以下详细列出了用法和句例，供你参考。
for 1 preposition
1
used to say who is intended to get or use something, or where something is intended to be used
I've got a present for you.
Someone left a message for Vicky.
2
in order to help someone or something
I looked after the kids for them.
Let me carry that bag for you.
3
used to say what the purpose of an object, action etc is
for doing something
a knife for cutting bread
What did you do that for?
4
in order to have, do, get, or obtain something
Are you waiting for the bus?
the qualifications necessary for a career in broadcasting
5
used to say how long an action or situation continues for
Bake the cake for 40 minutes.
We had been talking for a good half hour.