title: Nonabelian cohomology
text: # Nonabelian cohomology
  
  In mathematics, a nonabelian cohomology is any cohomology with coefficients in a nonabelian group, a sheaf of nonabelian groups or even in a topological space.
  
  If homology is thought of as the abelianization of homotopy (cf. Hurewicz theorem), then the nonabelian cohomology may be thought of as a dual of homotopy groups.
  
  ## Nonabelian Poincaré duality
  
  See: Nonabelian Poincare Duality (Lecture 8)
  
  