 ##  [Functional](/index.php/functional) 

  ##  [Functional](https://mathlogic.quantumdictionary.io/functional-0) 

  
 [![Mathematics & Logic Dictionary](/sites/default/files/styles/large/public/2026-01/Mathematics%20%26%20Logic.png.webp?itok=UhtTRPnp)](/index.php/topic-specific-dictionaries/natural-formal-sciences/mathematics-logic)

- Natural &amp; Formal Sciences -

**Mathematics &amp; Logic Dictionary**

 
Definition

A mapping from a space of functions to the real or complex numbers (or more generally to a field), often representing an evaluation, cost, or quantity to be optimized in variational problems.