18A40 18C20 adjoint functors pairing of functors 16.E99 16D90 16E50 16T1 16T15 Frobenius monads \(\tau\)-supplemented,\(\tau\)-complemented and \(\tau\)-semiperfect modules \(r\)-counital comonads \(r\)-unital monads cofirm comodules firm modules neat and coneat submodules proper classes separability weak (co)monads weak monads and comonads