The solidus (Latin 'solid'; pl. solidi) or nomisma (Greek: νόμισμα, nómisma, lit. 'coin') was a highly pure gold coin issued in the Late Roman Empire and Byzantine Empire. Constantine introduced the coin, and its weight of about 4.5 grams remained relatively constant for seven centuries. In the Byzantine Empire, the solidus or nomisma remained a highly pure gold coin until the 11th century, when several Byzantine emperors began to strike the coin with less and less gold. The nomisma was finally abolished by Alexius I in 1092, who replaced it with the hyperpyron, which also came to be known as a "bezant". The Byzantine solidus also inspired the originally slightly less pure dinar issued by the Muslim Caliphate. In Western Europe, the solidus was the main gold coin of commerce from late Roma