Quadrivium n. : The four "liberal arts," arithmetic, music, geometry, and astronomy; -- so called by the schoolmen. See Trivium.

Example:
Why are the astronomical symbols in the Quadrivium inverted?

Taxonomy
quadrivium, music, quantity, magnitude, free encyclopedia, arithmetic, geometry, astronomy, preparatory work, trivium, relationship, practised, Morris Kline, medieval universities, Pythagoreans, search, four ways, four roads.

Defination from the web:
quadrivium comprised the four subjects, or arts, taught in medieval universities after the trivium. ... The quadrivium consisted of arithmetic, geometry, music, and astronomy. ... In turn, the quadrivium was considered preparatory work for the serious study of philosophy and theology. ...