Ordinary Point

a_{2} (x) y^{″} + a_{1} (x) y^{'} + a_{0} (x) y = 0 ⊛

rewritten in standard form as

y^{″} + P (x) y^{'} + Q (x) y = 0

$x_{0}$ is an ordinary point of $⊛$ if $P (x)$ and $Q (x)$ are both analytic at $x_{0}$