Have you ever heard of Paul’s letters from the New Testament referred to as epistles? An epistle is actually like a letter. But unlike a letter which is meant to be sent to and read by another individual, an epistle is written for a large audience, and is to be read by and circulated by a large number of recipients. Though Paul does often speak to particular individuals in certain epistles they are mostly addressed to a larger audience.
So when someone refers to Paul’s letter to the Romans, you can now arrogantly inform them Paul wrote an epistle, not a letter. Just kidding 🙂
 J. Stephen Lang, 1001 Things You Always Wanted to Know About the Bible. (New York:NY Barnes & Noble, Inc. 2010) Pg 457.