Definition:Period of Periodic Real Function/Also known as

Period of Periodic Real Function: Also known as
The period of a periodic function $f$ is also known as the principal period of $f$, particularly by those sources which define a period of $f$ as any $L \in \R_{>0}$ such that:
 * $\forall x \in \R: \map f x = \map f {x + L}$

Some sources use the term fundamental period.