As everytime I have done a "Tetralogy" cover in the past, there has always been someone who asks why I used that word and not "Quadrilogy"?
Basically the 20th Century Fox marketing team coined the synonym "Quadrilogy" for the release of their Alien DVD box set
The Alien Quadrilogy. This uses the Latin numerical prefix quadri-/quadr- Instead of the usual Greek Tetra-.
Here is a list of "a/ologies" for their related number of films as per the Oxford English Dictionary.
- 2 in a series = Sequel or Duology
- 3 in a series = Trilogy
- 4 in a series = Tetralogy
- 5 in a series = Pentalogy
- 6 in a series = Hexology
- 7 in a series = Heptalogy
- 8 in a series = Octology
- 9 in a series = Nonology
- 10 in a series = Decology
Obviously these are to be used as a matter of preference and choice. I mean, I chose to use it on my "Tremors" cover as two "T" sounding words obviously flows better than using Fox's Quad one... Tremors Tetralogy IMO is vastly better than "Tremors Quadrilogy".
Anyway now you know the "a/ologies" I hope this clears things up and is of some use.
Regards
HOTD