\begin{definition}[Definition:Antiperiodic Function/Antiperiodic Element]
Let $f: X \to X$ be a function, where $X$ is either $\R$ or $\C$.
Let $L \in X_{\ne 0}$.
Then $L$ is an '''anti-periodic element''' of $f$ {{iff}}:
: $\forall x \in X: - \map f x = \map f {x + L}$
Category:Definitions/Antiperiodic Functions
\end{definition}