As a preposition
For is used to show who or what is intended to get or use something.
- I'm going to buy a birthday present for her.
- There's a letter for you from your wife.
- We need to buy some new furniture for the house.
- Is there enough food for everyone?
For is used to show a purpose, reason or cause.
- I read books for pleasure.
- a machine for making plastic plates.
- He was awarded a medal for bravery.
What...for is used to ask the purpose or reason for something
- What did you do that for? [=why did you do that?]
- What's this tool for?
For is used to say how long something happens.
For+a period of time
- We have lived in Chicago for two years.
- He has been ill for a long time.
- I haven't seen him for ages.
We use for to talk about a distance.
- We must have walked for miles.
- The beach stretches for over three kilometers.
For is used to say the cost of something
- I sold my car to David for $800.
- He bought the camera for $150.
We use for after verbs to form multi-word verbs. Phrasal verbs and prepositional verbs are multi-word verbs.
- He is still looking for a job.
- He cares for his elderly parents.
As a conjunction
We use for as a conjunction in formal situations. For is similar in meaning to because. It is used to connect two clauses.
- I went to bed early, for I was very tired.