Abstract: All the higher separation axioms in topology, except for complete regularity, are known to have sandwich-type characterizations. This note provides a characterization of complete regularity in terms of inserting a continuous real-valued function. The known fact that each continuous real valued function on a compact subset of a Tychonoff space has a continuous extension to the whole space is obtained as a corollary.

AMS Subject Classification: 54D15, 54D30, 54C30.