An obol (4 letters) was an ancient Greek silver coin, which was the smallest denomination of currency in circulation. A stater (6 letters) was a larger denomination of ancient Greek silver coin, and was worth two obols. The euro (4 letters) is the current official currency of the European Union, and is divided into 100 cents. The ecu (3 letters) was a former currency of the European Union, which was replaced by the euro in 1999.