Separating set

In mathematics, a set of functions with domain is called a and is said to if for any two distinct elements and of there exists a function such that
Separating sets can be used to formulate a version of the Stone–Weierstrass theorem for real-valued functions on a compact [Hausdorff space] with the topology of uniform convergence. It states that any subalgebra of this space of functions is dense if and only if it separates points. This is the version of the theorem originally proved by Marshall H. Stone.

Examples

The singleton set consisting of the identity function on separates the points of
If is a T1 normal topological space, then Urysohn's lemma states that the set of continuous functions on with real values separates points on
If is a locally convex Hausdorff topological vector space over or then the Hahn–Banach separation theorem implies that continuous linear functionals on separate points.