buy vs song

buy and song both are nouns.

Word	Noun	Adjective	Verb	Adverb
buy	Yes	No	Yes	No
song	Yes	No	No	No

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

Other hyponyms of buy include travel bargain.

buy (noun)	song (noun)
an advantageous purchase	the act of singing
	a short musical composition with words
	the characteristic sound produced by a bird
	a distinctive or characteristic sound
	a very small sum

buy (verb)	song (verb)
accept as true
obtain by purchase; acquire by means of a financial transaction
make illegal payments to in exchange for favors or influence
acquire by trade or sacrifice or exchange
be worth or be capable of buying