'Functional Programming' is a style of programming that constructs programs primarily through the use of functions. This approach emphasizes declarative programming, where development involves expressions or declarations rather than explicit statements.

In this paradigm, a function's output is solely dependent on its input parameters. Thus, invoking a function f with the same input x consistently yields the same result f(x). This differs from procedural programming, which may yield varying outcomes with the same inputs, depending on the program's state.