Gharbi et Zerguite, Mohamed et Amin2021-07-182021-07-182021http://dspace.univ-msila.dz:8080//xmlui/handle/123456789/25061In this dissertation, we rst recall the notions related to ordered sets and lattices. In a similar way, we study the notions of pseudo-ordered sets and trellises, and present some examples. We pay particular attention to the elimination of the property of transitivity.enOrdered sets, Pseudo ordered sets, Trellises, Contraction set.Thesis