The categories with noninvertible morphisms are studied analogously to the
semisupermanifolds with noninvertible transition functions. The concepts of
regular n-cycles, obstruction and the regularization procedure are introduced
and investigated. It is shown that the regularization of a category with
nonivertible morphisms and obstruction form a 2-category. The generalization of
functors, Yang-Baxter equation, (co-) algebras, (co-) modules and some related
structures to the regular case is given.