Tietze extension theorem
Also found in: Wikipedia.
Tietze extension theorem[′tēt·sə ik′sten·chən ‚thir·əm]
A topological space X is normal if and only if every continuous function of a closed subset to [0,1] has a continuous extension to all of X.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.