Some Remarks on Semigroup Presentations

Abstract

Let a semigroup A be given by generators a 1 , a 2 , … , a d and defining relations u 1 = v 1 , u 2 = v 2 , … , u e = v e between these generators, the u i , v i being words in the generators. We then have a presentation of A , and write The same generators with the same relations can also be interpreted as the presentation of a group, for which we write