C*-algebras Associative rings and algebras Banach spaces Decomposition theory for $Ĉ*$-algebras Functional analysis Groupoids Isometrics (Mathematics) Noncommutative dynamical systems Rings and algebras arising under various constructions Selfadjoint operator algebras ($Ĉ*$-algebras, von Neumann ($Ŵ*$- ) algebras, etc.) Smash products of general Hopf actions Twisted and skew group rings, crossed products