Comedy is tragedy plus time.
Drama is tragedy plus conventionally attractive people.
Romance is conventionally attractive people plus other conventionally attractive people who dislike each other at first.
Rom-coms are all of the above plus a major misunderstanding that would be easy to resolve if the conventionally attractive people could actually just get in the same room and communicate clearly for five minutes.
Teen movies are all of the above plus a makeover montage.
Thrillers are suspense plus explosions.
Mysteries are suspense plus dead bodies.
Horror is dead bodies plus live bodies that are about to become dead bodies.
Westerns are drama plus cowboy hats.
Fantasy is thrillers plus wizards.
Sci-fi is fantasy but the wizards are scientists.
Space operas are sci-fi minus gravity.
Period pieces are romance plus ball gowns.
Arthouse is unconventionally attractive people plus moody music plus symbolism you don’t quite understand but can’t ask about without feeling silly.
Biopics are mostly fiction plus a little bit of reality.
Documentaries are reality. But more interesting.
Dystopia is also reality. Just with different names and funny outfits.