Definition:Way Below Closure

Definition
Let $\struct {S, \preceq}$ be an ordered set.

Let $x \in S$.

The way below closure of $x$, denoted by $x^\ll$, is defined by
 * $x^\ll := \set {y \in S: y \ll x}$

where $y \ll x$ denotes that $y$ is way below $x$.