song vs serenade

song and serenade both are nouns.

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

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

song (noun)	serenade (noun)
the act of singing	a song characteristically played outside the house of a woman
a short musical composition with words	a musical composition in several movements; has no fixed form
the characteristic sound produced by a bird
a distinctive or characteristic sound
a very small sum

song (verb)	serenade (verb)
	sing and play for somebody