A semi-group in which any two right principal ideals intersect is left reversible: $\forall a,b, \in S\ \exists x,y \in S \ :\ ax = by$. A commutative semi-group is reversible, as $ab=ba$. A semi-group which is reversible and obeys the cancellation law can be embedded in a group, cf Imbedding of semi-groups.
|||A.H. Clifford, G.B. Preston, "Algebraic theory of semi-groups" , 1–2 , Amer. Math. Soc. (1961–1967)|
Reversible semi-group. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Reversible_semi-group&oldid=39357