Definition:Star Shaped Set

Definition
Let $V$ be a vector space over a field $K$.

Let $W \subseteq V$ be a subset of $V$.

Then $W$ is called a star shaped set :
 * $\forall x \in W: -x \in W$

where $-x$ is the negative of $x$.

Also known as
Sometimes one occurs the hyphenated form, i.e. star-shaped set.

A star shaped set is also known as a balanced set.