20 Library introduction [library]

20.3 Definitions [definitions]

20.3.19 replacement function [defns.replacement]

a non-reserved function whose definition is provided by a C++ program
[Note: Only one definition for such a function is in effect for the duration of the program's execution, as the result of creating the program ([lex.phases]) and resolving the definitions of all translation units ([basic.link]). end note]