The conjugacy problem in semigroups and monoids

We present an algorithmic approach to the conjugacy problems in monoids and semigroups, using rewriting systems. There is a class of monoids and semigroups that satisfy the condition that the transposi- tion problem and the left and right conjugacy problem are equivalent. The free monoid and the completely simple semigroups belong to this class. We give a solution to the conjugacy problem for monoids and semigroups in this class that are presented by a complete rewriting system that satisfies some additional conditions.