When the first edition of the Encyclopedic Dictionary of Mathematics appeared in 1977, it was immediately hailed as a landmark contribution to mathematics: "The standard reference for anyone who wants to get acquainted with any part of the mathematics of our time" (Jean Dieudonné, American Mathematical Monthly). "A magnificent reference work that belongs in every college and university library" (Choice), "This unique and masterfully written encyclopedia is more than just a reference work: it is a carefully conceived course of study in graduate-level mathematics" (Library Journal). The new edition of the encyclopedia has been revised to bring it up to date and expanded to include more subjects in applied mathematics. There are 450 articles as compared to 436 in the first edition: 70 new articles have been added, whereas 56 have been incorporated into other articles and out-of-date material has been dropped. All the articles have been newly edited and revised to take account of recent work, and the extensive appendixes have been expanded to make them even more useful. The cross-referencing and indexing and the consistent set-theoretical orientation that characterized the first edition remain unchanged, The encyclopedia includes articles in the following areas: Logic and Foundations; Sets, General Topology, and Categories; Algebra; Group Theory; Number Theory; Euclidean and Projective Geometry; Differential Geometry; Algebraic Geometry; Topology; Analysis; Complex Analysis; Functional Analysis; Differential, Integral, and Functional Equations; Special Functions; Numerical Analysis; Computer Science and Combinatorics; Probability Theory; Statistics; Mathematical Programming and Operations Research; Mechanics and Theoretical Physics; History of Mathematics. Kiyosi Ito is professor emeritus of mathematics at Kyoto University.