tetralogy

noun4

1. •
   A set of four works of art that are connected, and that can be seen either as a single work or as four individual works. They are commonly found in literature, film, or video games.
2. •
   (historical) A group of four dramas, three tragic and one satiric, exhibited together at the festivals of Dionysus at Athens.
3. •
   A combination of four symptoms.
4. •
   (informal) Tetralogy of Fallot.