\begin{definition}[Definition:Positive Definite Functional]
Let $f : S \to T$ be a mapping.
Let $f \in \MM$, where $\MM$ stands for some function space.
Let $F \sqbrk f : \MM \to \R$ be a real-valued functional.
Suppose:
:$\forall f \in \MM: F \sqbrk f > 0$
Then $F$ is a '''positive-definite functional'''.
Category:Definitions/Functional Analysis
\end{definition}