The structure of regular semigroups is studied in full generality. The principal tool used in this is the concept of a (regular) biordered set which abstractly characterizes the set of idempotents of a regular semigroup. The category of inductive groupoids is then defined as the category whose objects are pairs consisting of an ordered groupoid and an order-preserving functor of the chain groupoid of a biordered set whose vertex map is a bijection, and whose morphisms are certain commutative diagrams in the category of ordered groupoids. It is shown by an explicit construction that every regular semigroup can be constructed from an inductive groupoid and that the category of inductive groupoids is equivalent to the category of all regular semigroups. This construction is then applied to obtain the structure of all fundamental regular semigroups and all idempotent generated regular semigroups. The paper ends with a study of biordered sets of some important classes of regular semigroups.

This work offers concise coverage of the structure theory of semigroups. It examines constructions and descriptions of semigroups and emphasizes finite, commutative, regular and inverse semigroups. Many structure theorems on regular and commutative semigroups are introduced.;College or university bookstores may order five or more copies at a special student price which is available upon request from Marcel Dekker, Inc.