Let $X$ be a (real) vector space.
Let $S$ be a nonempty subset of $X$.
If $S$ is closed under addition and scalar multiplication,
then we call $S$ a subspace.
If $S$ is closed under multiplication by nonnegative scalars,
then we call $S$ a cone (that may or may not be convex).
My question is:
What do we call $S$ if $S$ is closed under scalar multiplication?
Note: $S$ need not be closed under addition.