A submodule that is not the entire module.
Proper Submodule
See also
Irreducible Module, SubmoduleThis entry contributed by Margherita Barile
Explore with Wolfram|Alpha
Cite this as:
Barile, Margherita. "Proper Submodule." From MathWorld--A Wolfram Web Resource, created by Eric W. Weisstein. https://mathworld.wolfram.com/ProperSubmodule.html