The group cohomology 
of a group 
with coefficients in a 
-module 
is the right derived functor
of the invariant-module functor 
. Low-dimensional groups classify invariant elements,
derivations modulo principal derivations, and extensions.
Group Cohomology
See also
Cohomology Group, Derived Functor, Group, ModuleExplore with Wolfram|Alpha
References
Brown, K. S. Cohomology of Groups. New York: Springer-Verlag, 1982.Cite this as:
Weisstein, Eric W. "Group Cohomology." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/GroupCohomology.html