Ibrahim, G. R.Bakare, G. N.2020-02-202020-02-202013Ibrahim G. R. and Bakare, G. N., (2013): Some properties of symmetric inverse semigroup and some of its subsemigroup.http://hdl.handle.net/123456789/3819In this paper, we studied the number of nilpotent element of order preserving one-one partial transformation semigroups and number of nilpotent elements of order decreasing + order preserving one-one partial transformation semigroups. Also, we shower that every idempotent element of one-one partial transformation semigroup is a contraction mapping.enSemigroup,Symmetric inverse semigroup,order preservingNilpotentorder decreasingSubsemigroupIdempotent elements,Article