Abstract
In this note all rings R are associative with identity, all modules are unitary right modules and we denote the category of all such R-modules by Mod-R. Let M ⊆ Mod-R and A ∊ M. Corational submodules of A in M are defined and studied. Examples of modules M for which every submodule has a smallest corational submodule in M and an example of a module M with a submodule A which has no minimal corational submodule in M are given. In the second half of the paper copolyform modules are defined and we characterize when a finite direct sum of weakly supplemented copolyform modules is copolyform.