Defined in header
#define imaginary _Imaginary
This macro expands to a type specifier used to identify imaginary complex types. The macro is defined only if the implementation supports imaginary types.
|This section is incomplete|
Reason: on what condition? The standard seems unclear. Maybe when __STDC_IEC_559_COMPLEX__ is defined?
A program may undefine and perhaps then redefine the imaginary macro.
 See also
| complex type macro |