Coin collectors call one side of a coin 'obverse'. What do they call the other side of a coin?

Coin collecting has its own lexicon. These words help collectors accurately discuss coins.

The parts of a coin are important to know for both describing coins and understanding what other people are saying about them. A coin has 2 sides, or faces. Most people just call these "front" and "back", or "heads" and "tails", but the correct terms are obverse (front/heads) and reverse (back/tails). For most coins the obverse is the "heads" side - the side with a picture of a person, or animal, or coat-of-arms - and the reverse is the "tails" side. For coins that don't have an obvious obverse or reverse, I'm unsure how you pick which is the "front" and which is the "back". A coin also has an edge, which is the (usually) flat part that runs around the circumference of the coin. Sometimes the edge of a coin can be as distinctive as its obverse or reverse - keep an eye out for coins that have words, symbols, or a design on their edge (like the United States' Presidential $1 coins).