The way I like to think about this is Rick Altman's Sementic/Syntactic approach to genre. (a short summary here: https://introfilmgenres.wordpress.com/2014/09/0

The way I like to think about this is Rick Altman's Sementic/Syntactic approach to genre. (a short summary here: https://introfilmgenres.wordpress.com/2014/09/09/the-semanticsyntactic-approach-and-genre-development/ https://introfilmgenres.wordpress.com/2014/09/09/the-semanti... ) Basically there are stock elements like space, lasers, aliens, etc. and there are thematic elements like themes of futurism, exploration, paradoxes, what is live? (these are just the ones I came up with off the top of my head) and just because a work has one of these doesn't make it part of that genre. Apollo 13 is set (largely) in space but I don't think people would call it science fiction. Star Wars is set in space but I have seen it argued thematically it is a western. (I think in the book Film/Genre Altman added a third category but I don't remember it and thought the book was pretty confusing compared to the initial article he wrote.)