For the preposition or conjunction

For is usually a preposition and rarely a coordinating conjunction.  

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. 

For+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.