Title: The T-functor of J. Lannes Author: Clarence W. Wilkerson Classification: 55P99 (55M35 55R35 55S10 55T15) Address: Dept. Math., Purdue University, West Lafayette, IN 47907-1395 This is a preliminary version of a two page expository article on the Lannes' T-functor for upcoming the Kluwer Encylopedia of Mathematics. Please send comments/corrections/improvements to wilker at math.purdue.edu 03/05/99