fluid drive vs coupling

fluid drive and coupling both are nouns.

Word	Noun	Adjective	Verb	Adverb
fluid drive	Yes	No	No	No
coupling	Yes	No	No	No

As nouns, coupling is a hypernym of fluid drive; that is, coupling is a word with a broader meaning than fluid drive:

fluid drive: an automotive power coupling
coupling: a mechanical device that serves to connect the ends of adjacent objects

Other hypernyms of fluid drive include coupler.

fluid drive (noun)	coupling (noun)
an automotive power coupling	the act of pairing a male and female for reproductive purposes
	a mechanical device that serves to connect the ends of adjacent objects
	a connection (like a clamp or vise) between two things so they move together