Nomisma

Nomisma: Lat. solidus, the gold coin introduced by Constantine I which remained the basis for the Byzantine precious metal coinage until the Latin conquest in 1204. Weighing 4.5g, it was reckoned at 24 keratia, a unit of account (carat), and its fractions were 12 silver hexagrams or milliaresia and 288 copper folleis. From the middle of the 11th century increasingly depreciated, it was reformed by Alexios I, and more commonly known thereafter as the nomisma hyperpyron or simply hyperpyron.