You can find most popular coin collecting phrases in this coin glossary.
half eagle - another name for a United States $5.00 gold coin. (See eagle and double eagle.)
hub - coin production term used to refer to a reverse design that is used to make the dies that strike the coins. Sometimes a punch that is used to stamp the design into the coin die.
hairlines - very light lines or scratches on the surface of a coin. Sometimes caused by light cleaning or polishing.
hammer die - top die. The hammer die is the top die that is placed on top of the coin blank and struck. Years ago this was done with a hammer. See "anvil die" and "die".
head - the obverse or front of most coins. Usually with a portrait of someone but not always.