Duality of St-closed submodules and semi-extending modules
CSt-closed submodules
St-closed submodules
Cosemi-essential submod-
ules
semi-essential submodules
Cosemi-extending modules
semi-extending modules.
The main goal of this paper is to dualize the two concepts St-closed submodule and semi-extending module which were given by Ahmed and Abbas in 2015. These dualizations are called CSt-closed submodule and cosemi-extending mod- ule. Many important properties of these dualizations are investigated, as well as some others useful results which mentioned by those authors are dualized. Furthermore, the relationships of cosemi-extending and other related modules are considered.
