quaternity, four, tetrad, quartet, quaternion, square, quarter. [planar form with four sides] tetract, tetragon, quadrangle, rectangle. [three dimensional object with four surfaces] tetrahedron. quadrature, quadrifoil, quadriform, quadruplet
quatrefoil. [object or animal with four legs] tetrapod. [geographical area with four sides] quadrangle, quad [Coll.]. [electromagnetic object] quadrupole. [four fundamental studies] quadrivium.