Convex cone
= Convex cone
{wiki}
A convex cone is a subset $C$ of a real <vector space> closed under nonnegative <linear combinations>: $ax+by\in C$ whenever $x,y\in C$ and $a,b\geq0$. The <positive semidefinite cone> and the <copositive cone> are examples, ordered by inclusion through the <positive-semidefinite-plus-nonnegative cone>.