Preposition:
* Reason or purpose: "I went to the store for milk."
* Duration or time: "He worked there for five years."
* Recipient or beneficiary: "This is for you."
* Exchange or trade: "I traded my old phone for a new one."
* Direction or destination: "He headed for the mountains."
* Part of a whole: "I need two cups for the recipe."
Conjunction:
* Because: "I stayed home for I was sick."
* In order to: "He studied hard for he wanted to get good grades."
* Since: "I've been living here for ten years."
* Despite: "He went out for it was raining."
Other uses:
* To indicate possession: "This is a book for my brother."
* To express support or favor: "I'm for the new policy."
* To indicate a preference: "I'd rather stay home for the weekend."
* As a placeholder: "He's looking for a job."
The specific meaning of "for" will be determined by the context in which it is used.