In reply to:

Well, I'm guessing now...
4 = Quadrology or quadrilogy ?
5 = Quintology or quintilogy ?
6 = Sextology or sextilogy ?
Help! This is confusing.



jabba,
At the risk of sounding rude, why did you post the question if you were going to ignore the first, best and only sensible answer you got, namely, from tsuwm:

tetralogy = 4 works
pentalogy = 5 works?

Check these two words out in http://www.onelook.com/ and you will find that they return the definitions you were expecting. Your alternatives above do not.