simplex
n//sɪmˈplɪsiə//simplex
(algebraic, _, topology, geometry) A generalization of a triangle or tetrahedron to an arbitrary dimension, the generalization being the simplest possible convex polytope for a given dimension; more accurately, the convex hull of n+1 affinely independent points in n-dimensional space.
A word which is not compound and contains no derivational affixes (inflectional affixes are usually disregarded); a monomorphemic word.