body of water vs falls

body of water and falls both are nouns.

Word	Noun	Adjective	Verb	Adverb
body of water	Yes	No	No	No
falls	Yes	No	No	No

As nouns, falls is a hyponym of body of water; that is, falls is a word with a more specific, narrower meaning than body of water:

body of water: the part of the earth's surface covered with water (such as a river or lake or ocean)
falls: a steep descent of the water of a river

body of water (noun)	falls (noun)
the part of the earth's surface covered with water (such as a river or lake or ocean)	a steep descent of the water of a river
	the petals or sepals of a flower that bend downward (especially the outer perianth of an iris)