A function whose range is in the real numbers is said to be a real function, also called a real-valued function.
Real Function
See also
Complex Function, Function, Real Variable, Scalar Function, Vector FunctionExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Real Function." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/RealFunction.html