This note is merely to introduce a new notion of complexity which extend the well-accepted notion of NP, co-NP and P. I believe that this new notion will be extremely helpful to distinguish easy enumeration problems from hard enumeration problems. Analysis of various enumeration problems in terms of the classes ENP, EP and CEP has been done by the author, and will be published in near future. Also, I have been working with Tomomi Matsui and Yasuko Matsui, to make a catalog of known enumeration algorithms for various combinatorial or geometric problems, which is not complete but partly available via WWW, see [FMM96].