connexion vs hookup

connexion and hookup both are nouns.

Word	Noun	Adjective	Verb	Adverb
connexion	Yes	No	No	No
hookup	Yes	No	No	No

As nouns, hookup is a hyponym of connexion; that is, hookup is a word with a more specific, narrower meaning than connexion:

connexion (noun)	hookup (noun)
the act of bringing two things into contact (especially for communication)	a system of components assembled together for a particular purpose
shifting from one form of transportation to another	a device providing a connection between a power source and a user
an instrumentality that connects
the process of bringing ideas or events together in memory or imagination
a relation between things or events (as in the case of one causing the other or sharing features with it)
a connecting shape