Certain Types Of Ordered Semigroups

This paper is composed of three chapters.Chapter 1 is introuduction and prelimilaries.In chapter 2, we give some properties of subidempotents, left regular ordered semigroups and maximal left ideals. We give characterizations of ordered semigroups without subidempotent and whose proper left ideals are Archimedean (1-Archimedean) ordered semigroups.In chapter 3, we study nil-extensions of some ordered semigroups on the base of nil-extensions of some semigroups, such as nil-extensions of Archimedean ordered semigroups, nil-extensions of (left)simple ordered semigroups and completely Archimedean ordered semigroups.