15 Library introduction [library]

15.3 Definitions [definitions]

15.3.20 program-defined type [defns.prog.def.type]

class type or enumeration type that is not part of the C++ standard library and not defined by the implementation, or an instantiation of a program-defined specialization
[Note
:
Types defined by the implementation include extensions ([intro.compliance]) and internal types used by the library.
end note
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