A complex rational
function (or rational
function, or fractional
function) in $\C $ is a function $f: \C
\to \C $ for which there exists polynomials $p:
\C \to \C $ and $q: \C \to \C $ in $\C $ so
that
\[
f(z) = \frac{p(z)}{q(z)},
\]