The word for can be used as a preposition and a conjunction. As a preposition, it is followed by a noun.
- Let’s buy some flowers for mummy.
- I waited for hours, but she didn’t come.
As a conjunction, for is used to connect two clauses. A for-clause usually shows cause/reason.
- I asked him to turn the music down, for I wanted to sleep.
A for-clause is not very common in this context and it sounds too formal. In an informal style, we are more likely to express the same idea with because.
- I asked him to turn the music down because I wanted to sleep.
A for-clause may also express an inference.
- She must have gone to bed for there is no light in her room.
As a preposition for is used to express several ideas. For example, it can be used to indicate purpose, destination, duration etc. It may also be used to express your liking, suitability or skill for something.
- I have bought a gift for you.
- What can I do for you?
- The college provides vocational training for young boys and girls.
- Thousands of people have sacrificed their lives for the country.
For can indicate duration.
- It has been raining for hours.
- I have been waiting for 20 minutes.
For cannot be used with a verb to indicate purpose. The infinitive alone is used to express a person’s purpose.
- I went to the college to see Professor Charles. (NOT I went to the college for seeing Professor Charles.)
However, for can be used with an –ing form to indicate the purpose of a thing.
- A thermometer is used for measuring temperature.
When the clause has a person as subject, we are more likely to use an infinitive.
- We use a thermometer to measure temperature.