46-XX Functional analysis {For manifolds modeled on topological linear spaces, see 57Nxx, 58Bxx} 137188
46Cxx Inner product spaces and their generalizations, Hilbert spaces {For function spaces, see 46Exx} 5386
46C20 Spaces with indefinite inner product (Kreĭn spaces, Pontryagin spaces, etc.) [See also 47B50] 888