We can use "will" to talk about the future. We also use will to make predictions, talk about decisions, and to make promises, offers, requests and threats.
Grammar rules
"Will" and the negative form "will not" or "won't" is a modal auxiliary verb.
This means that there is no s on the third person singular, and that it is followed by the infinitive:
I will leave later.
You will leave later.
He / she will leave later.
We will leave later.
They will leave later.
Note: "will" is often abbreviated to 'll in spoken English:
"I'll leave later."
"He'll leave later."
To make the question form, change the word order:
"You will leave later" = "Will you leave later?"
(For more information on the grammar of modal auxiliary verbs, see our page on how to use "can".)