Disk of convergence
= Disk of convergence
{title2=$\{z\in\mathbb C:|z-c|<R\}$}
For a <power series> centred at $c$ with <radius of convergence> $R$, its disk of convergence is the open <disk> $|z-c|<R$, on which the <series> has <absolute convergence>. Boundary points may or may not belong to the larger <domain of convergence>. When $R=0$ this open <disk> is empty, although the <power series> still converges at its centre; when $R=\infty$ it is the whole <complex plane>.