[: More must be said here about the complex functions' ranges.]

#include <math.h>
float sinhf(float a);
double sinh(double a);
long double sinhl(long double a);

#include <complex.h>
float complex csinhf(float complex a);
double complex csinh(double complex a);
long double complex csinhl(long double complex a);

#include <tgmath.h>
floating-type sinh(floating-type a);

The sinh functions take a hyperbolic angle a and return the hyperbolic sine of that angle, sinh a.

#include <math.h>
float asinhf(float r);
double asinh(double r);
long double asinhl(long double r);

#include <complex.h>
float complex casinhf(float complex r);
double complex casinh(double complex r);
long double complex casinhl(long double complex r);

#include <tgmath.h>
floating-type asinh(floating-type r);

The asinh functions take a ratio r and return the area hyperbolic sine of that ratio, sinh⁻¹ r.