Semientwining structures are proposed as concepts simpler than entwining structures, yet they are shown to have interesting
applications in constructing intertwining operators and braided algebras, lifting functors, finding solutions for Yang-Baxter systems,
and so forth. While for entwining structures one can associate corings, for semientwining structures one can associate comodule
algebra structures where the algebra involved is a bialgebra satisfying certain properties.