Fix a ring R and let M be a module. The following conditions are equivalent:
- The module M satisfies an ascending chain condition on the set of its submodules: that is, there is no infinite strictly ascending chain of submodules .
- Every submodule of M is finitely generated.
- Every nonempty set of submodules of M has a maximal element when considered as a partially ordered set with respect to inclusion.
When the above conditions are satisfied, M is said to be Noetherian.
- A zero module is Noetherian, since its only submodule is itself.
- A Noetherian ring (satisfying ACC for ideals) is a Noetherian module over itself, since the submodules are precisely the ideals.
- A free module of finite rank over a Noetherian ring is a Noetherian module.
- A free module of infinite rank over an infinite set is not Noetherian.