What Makes A Coin 'Rare'?

What makes a coin 'rare'?
full Coin World article:
http://www.coinworld.com/news/022006/BW_0220.asp

Knowing full history helps provide answers
posted 2/7/06
By Paul Gilkes
Coin World Staff

No single factor determines rarity. Many factors have to be considered before declaring a coin "rare."

A few of the factors that can lead to a coin being considered rare are total mintage; normal or abnormal attrition as a result of circulation, accidental loss or destruction, and official and private meltings; and the level of public and collector interest in a coin at the time it is being released into circulation.

Remember, however, that "rare" is relative. So, too, is value; a rare coin may not necessarily be valuable if no or little collector market exists for it.