Circulum
Circulum is a Latin noun meaning "a circle" or "a ring." In classical Latin, circulum appears as the accusative singular form of circulus, a term used to describe circular figures, circumferences, or circular paths in mathematical, astronomical, and rhetorical contexts. The root circul- gives rise to a family of related terms in many Romance languages and in English derivatives such as circle, circuit, and circular.
In scholarly usage, circulum is encountered mainly in descriptions of diagrams, geometrical figures, or orbital paths,
In modern English-language scholarship, circulum is rarely used as a technical term outside discussions of Latin