Functional analysis Mathematics 25 Functions of real variables 9 Measure theory 9 Operator theory 5 Functions of complex variables 4 Topology 4 Functional Analysis 3 Functional analysis -- Instructional exposition (textbooks, tutorial papers, etc.) 3 Functions 3 Metric spaces 3 Approximation theory 2 Approximations and expansions 2 Differential equations, Partial 2 Functions of a Complex Variable 2 Functions of a complex variable 2 Harmonic analysis on Euclidean spaces 2 Integration, Functional 2 Mathematical optimization 2 Measure and integration -- Instructional exposition (textbooks, tutorial papers, etc.) 2 Nonlinear functional analysis 2 Number theory 2 Probability theory and stochastic processes 2 Real Functions 2 Real functions 2 Several Complex Variables and Analytic Spaces 2 Algebra 1 Algebraic Geometry 1 Algebraic geometry 1 Algebras, Linear 1