Some Remarks on Semigroup Presentations

Abstract

Let a semigroup A be given by generators a1, a2, … , ad and defining relations u1 = v1, u2 = v2, … , ue = ve between these generators, the ui, vi being words in the generators. We then have a presentation of A, and writeThe same generators with the same relations can also be interpreted as the presentation of a group, for which we write