Alloy- A mixture of two or more metals.
Base Metal- An inexpensive metal; a metal other than gold, silver, or platinum.
Billion- Gold or silver alloyed with a large amount of lesser metal, such as copper, tin, or zinc.
Bit- One eighth of Spanish milled dollar; 12 1/2 cents.
Blank- A piece of metal that is to be struck as a design.
Bust- The head and upper portion of the body.
Bullion- Metal in a bulk form; bars of metal.
Clad Coins- Coins that are composed of three layers of metal bonded together.
Clipped Coins- A coin from which some of the metal has illegally cut or shaved, usually around the edges.
Commemorative Coin- A coin issued to honor a person, place, or historical event.
Corrugated Edge- The edge of a coin stamped with vertical lines; a receded edge
Countermark- A marked stamp over an existing design, changing its value or making it current in another country.
Die- A metal stamp bearing a design; used to strike a coin.
Double Struck- A blurred design on a coin caused by striking the coin twice.
Debasement- Lowering the purity of a metal by adding a cheaper metal.
Electrum- A natural mixture of gold and silver.
Face- The Obverse side of a coin containing the principal design.
Face Value- The value stated on the coin.
Fasces- A bundle of wooden rods tied together with a thong with an axe blade in the center.
Field- The blank background on a coin that is not occupied by the design.
Flan- The blank metal used to make a coin; planchet.
Hoard- A hidden stock of coins.
Incuse- A design sunk into a coin as opposed to a raised design.
Inscription- All letters, words, or numbers appearing on a coin.
Key Coin- A hard-to-get coin needed to complete a collection.
Legal Tender- Money that must be accepted by law as a payment in financial transaction.
Legend- Words appearing on the surface of a coin along the curved edge.
Lettered Edge- Letters that appeared around the narrow, up-and-down edge of earlier coins, the purpose was to prevent clipping.
Milled Edge- The thin rim around a coin that forms a raised border.
Mint Mark- A small letter or symbol on a coin to indicate where it was struck.
Numismatics- The science or study of coins and currency of all kinds.
Obverse- The "head" side of a coin which usually bears the date.
Overstrike-A new design that has been struck over an earlier one.
Patina- A tone or coloring found on some coins caused by action of the air.
Planchet- The blank metal disk from which a coin is struck; also called a blank or flan.
Proof- A coin especially struck for collectors.  It usually has a mirror like finish; a coin having a frosty surface is called a matte proof.
Reeded Edge- Vertical markings around the edge of a coin to prevent clipping; also called a corrugated or grained edge.
Relief- A design that is raised above the coin.  The designs on an American penny, and the American dime are in relief.
Restrike- A coin struck at a later date from original dies.
Reverse- The back or "tail" side of a coin.
Series- Coins of a single type such as the Roosevelt Dime series.
Token- A piece struck by private individuals or companies in imitation of a coin to be used for advertising or as a medium of exchange in transactions with that company.