What is an inverse system? Here are some definitions.
Noun
(algebra) An indexed family of groups whose index set is a directed poset, together with a set of homomorphisms which are indexed by a subset of the Cartesian product of the index set with itself — which subset corresponds to the ordering relation of the directed poset — such that the domain and codomain of each homomorphism is obtained by reversing its ordered pair of indexes
(category theory) A generalization of the above definition, where groups are replaced by objects, and homomorphisms are replaced by morphisms.
