Face of a convex set
= Face of a convex set
= Convex face
{synonym}
A <convex set> $F\subseteq C$ is a face of $C$ if $ty+(1-t)z\in F$, with $y,z\in C$ and $0<t<1$, implies $y,z\in F$. A singleton face is an <extreme point>. A face of a face is a face of the original <convex set>.