Definition of Value (mathematics)

In mathematics, value commonly refers to the 'output' of a function. In the most basic case, that of unary, single-valued functions, there is one input (the argument) and one output (the value of the function).

Example: If the function is defined by prescribing that for each real number , then the input 3 will yield the function value 10 (since indeed ).

The function of the example is real-valued, since each and every possible function value is real. On the other hand, it is not injective, since different inputs may yield the same value; e.g., , too.