coupling vs swivel

coupling and swivel both are nouns.

Word	Noun	Adjective	Verb	Adverb
coupling	Yes	No	No	No
swivel	Yes	No	Yes	No

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

coupling: a mechanical device that serves to connect the ends of adjacent objects
swivel: a coupling (as in a chain) that has one end that turns on a headed pin

Other hyponyms of coupling include clevis, clutch, fluid drive, turnbuckle, universal, universal joint.

coupling (noun)	swivel (noun)
the act of pairing a male and female for reproductive purposes	a coupling (as in a chain) that has one end that turns on a headed pin
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

coupling (verb)	swivel (verb)
	turn on a pivot