negligible function

a function $f:\mathbb{N}\to {\mathbb{R}}_{\ge 0}$ is neglibile if for every polynomial $p$ there is an integer $N$ such that for all $n>N$, $f(n)<\frac{1}{p(n)}.$

this means that its output converges to zero faster than the inverse of any polynomial.

it is normally written as negl.