Fivology?

A series of three works is well known as a trilogy. Sometimes life seems to come in threes (or not), and we certainly have given symbolic significance to sets of three, interior design, storytelling, and comedy. Trilogies are everywhere. Douglas Adams referred to the fifth work in his Hitchhiker's Guide to the Universe series, "Mostly Harmless," as, "the fifth book in the increasingly inaccurately named trilogy." Well, we tend to label everything and there so happens to actually be a name for that. A series of five works is a pentalogy. To label a numbered series really is as easy as substituting the appropriate Greek numerical prefixes: duology, trilogy, quadology, pentalogy, hexalogy, heptalogy, octalogy, ennealogy, decalogy...