 Star domain

In mathematics, a set "S" in the Euclidean space R"n" is called a star domain (or star-convex set, star-shaped set or radially convex set) if there exists an "x"0 in "S" such that for all "x" in "S" the line segment from "x"0 to "x" is in "S".This definition is immediately generalizable to any real or complex vector space.