plateau

A plateau of a function is a region where a function has constant value.

More formally, let $U$ and $V$ be topological spaces. A plateau for a scalar function $f:U\to V$ is a path-connected set of points $P\subseteq U$ such that for some $y$ we have

$$\forall p\in P,f(p)=y$$(1)

Please take note that this entry is not authoritative. If you know of a more standard definition of “plateau”, please contribute it, thank you.