Definition:Power Series/Center

Definition
Let $\displaystyle \sum_{n \mathop = 0}^\infty a_n \left({x - \xi}\right)^n$ be a power series.

The point $\xi$ is the center of $\displaystyle \sum_{n \mathop = 0}^\infty a_n \left({x - \xi}\right)^n$.

Linguistic Note
British English spells this centre.

The convention on is to use the American English spelling center, but it is appreciated that there may be lapses.