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