Collectionwise Hausdorff space

In mathematics, in the field of topology, a topological space formula_1 is said to be collectionwise Hausdorff if given any closed discrete subset of formula_1, there is a pairwise disjoint family of open sets with each point of the discrete subset contained in exactly one of the open sets. 
Here a subset formula_3 being "discrete" has the usual meaning of being a discrete space with the subspace topology (i.e., all points of formula_4 are isolated in formula_4).