3 Terms and definitions [intro.defs]

3.9[defns.character]character

⟨library⟩ object which, when treated sequentially, can represent text
[Note 1: 
The term does not mean only char, char8_t, char16_t, char32_t, and wchar_t objects ([basic.fundamental]), but any value that can be represented by a type that provides the definitions specified in [strings], [localization], [input.output], or [re].
— end note]