A branch of mathematics in which one studies the general properties of functions (cf. Function). Function theory splits into two parts: the theory of functions of a real variable and the theory of functions of a complex variable (cf. Functions of a real variable, theory of; Functions of a complex variable, theory of).
Function theory. Encyclopedia of Mathematics. URL: http://www.encyclopediaofmath.org/index.php?title=Function_theory&oldid=12418