Editing Functional (mathematics) (section)

==Functional equations==
{{Main|Functional equation}}

The traditional usage also applies when one talks about a functional equation, meaning an equation between functionals: an equation <math>F = G</math> between functionals can be read as an 'equation to solve', with solutions being themselves functions. In such equations there may be several sets of variable unknowns, like when it is said that an [[Additive map|''additive'' map]] <math>f</math> is one ''satisfying [[Cauchy's functional equation]]'': 
<math display=block>f(x + y) = f(x) + f(y) \qquad \text{ for all } x, y.</math>