in law, the concept of law in ancient Greek philosophy. The problems of political authority and the rights and obligations of citizens were a major concern in the thought of the leading Greek Sophists of the late 5th and early 4th centuries BC. They distinguished between nature (physis) and convention (nomos), putting laws in the latter category. Law generally was thought to be a human invention arrived at by consensus for the purpose of restricting natural freedoms for the sake of expediency and self-interest. This view of law as arbitrary and coercive was not conducive to social stability, however, and thus was amended by Plato and other philosophers, who asserted that nomos was, or at least could be, based upon a process of reasoning whereby immutable standards of moral conduct could be discovered, which could then be expressed in specific laws. The dichotomy between the negative and positive views of law was never actually resolved.

in music, class of traditional melodies used by ancient Greek epic singers, often with lyre accompaniment. The nomos was an important art form for professional soloists, especially in musical competitions. Nomoi were in three, five, or seven movements and originally in a single harmonia. There were no strophic repetitions.

Nomoi were also performed on the kithara (lyre) and the aulos (double-piped oboe). Best known is the five-movement nomos depicting Apollo's victory over the dragon, played on an aulos at Delphi in 586 BC.