High Quality Content by WIKIPEDIA articles! High Quality Content by WIKIPEDIA articles! In mathematics, in the theory of modules, the radical of a module is a component in the theory of structure and classification. Let R be a ring and M a left R-module. A submodule N of M is called cosimple or maximal if the quotient M/N is a simple module. In abstract algebra, the concept of a module over a ring is a generalization of the notion of vector space, where instead of requiring the scalars to lie in a field, the "scalars" may lie in an arbitrary ring.