buoy vs nun buoy

buoy and nun buoy both are nouns.

Word	Noun	Adjective	Verb	Adverb
buoy	Yes	No	Yes	No
nun buoy	Yes	No	No	No

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

buoy: a float attached by rope to the seabed to mark channels in a harbor or underwater hazards; typically brightly-coloured
nun buoy: a buoy resembling a cone

Other hyponyms of buoy include acoustic buoy, can, can buoy, conical buoy, nun, spar buoy.

buoy (noun)	nun buoy (noun)
a float attached by rope to the seabed to mark channels in a harbor or underwater hazards; typically brightly-coloured	a buoy resembling a cone