Nondecreasing Function

A function $f(x)$ is said to be nondecreasing on an Interval $I$ if $f(b)\geq f(a)$ for all $b>a$, where $a,b\in I$. Conversely, a function $f(x)$ is said to be nonincreasing on an Interval $I$ if $f(b)\leq f(a)$ for all $b>a$ with $a,b\in I$.

See also Decreasing Function, Nonincreasing Function