ABSTRACT
Simple modules are those with no non-trivial submodules. They are to be regarded as basic building blocks in module theory. We already have encountered them in different places. In this chapter we are going to investigate direct sums of simple modules (semisimple modules) and to study the question of how arbitrary modules are connected with semisimple modules (socle, radical). In a certain sense dual to semisimple modules are the co-semisimple modules introduced at the end of this chapter.
