'Letter' in the Bible

I wrote to you in a letter not to associate with sexually immoral people.

But the sense of my letter was that if a brother had the name of being one who went after the desires of the flesh, or had the desire for other people's property, or was in the way of using violent language, or being the worse for drink, or took by force what was not his, you might not keep company with such a one, or take food with him.

Now, as to the things in your letter to me: It is good for a man to have nothing to do with a woman.

When I arrive, I will send with letters those you recommend to carry your gracious gift to Jerusalem.