This question has been touched on in other questions but not answered in a way that fully answers my own question. Like here:
To put my idea in everyday terms it is "Fleas are a type of parasite, but parasites are not a type of flea". That is, there is a super-set (parasites) and a sub-set (fleas); a hierarchy. Does the statement have a name of any sort? (I'm not looking for a fallacy.)
Thanks in advance.