The purpose of this paper is to present some dual properties of dual
comodule. It turns out that dual comodule has universal property
(cf.Theorem 2). Since (( )∗,( )o) is an adjoint pair
(cf.Theorem 3), some nice properties of functor
( )o are obtained. Finally Theoram 4 provides that the cotensor product is
the dual of the tensor product by (M⊗AN)o≅Mo◻AoNo. Moreover, the result HomA(M,N)≅ComAo(No,Mo) is proved for finite related modules M,N over a reflexive
algebra A.