Cofinitely supplemented modules

ABSTRACT In this thesis, we defined Cofinitely Supplemented Modules and investigated main properties of Cofinitely Supplemented Modules, e.g. "arbitrary sum of cofinitely supplemented modules is cofinitely supplemented." Or, "every maximal submodule of a module M has a supplement if and only if every cofinite submodule ha s asupplement. We also proved that the ring R is Semiperfect if and only if every R- module is cofinitely supplemented. For a non-local Dedekind Domain R, an R- module M is amply cofinitely supplemented if and only if M is injective or Torsion.