Regular function
= Regular function
A regular function on an open subset $U$ of a <scheme> $X$ is a section of $\mathcal O_X(U)$. On an affine variety it is locally a quotient of polynomial functions with a denominator that does not vanish.
On a variety, a regular function is a <regular map> to the <affine line>; the arbitrary-target regular-map concept is broader.