serpent vs worm snake

serpent and worm snake both are nouns.

Word	Noun	Adjective	Verb	Adverb
serpent	Yes	No	No	No
worm snake	Yes	No	No	No

As nouns, worm snake is a hyponym of serpent; that is, worm snake is a word with a more specific, narrower meaning than serpent:

Other hyponyms of serpent include colubrid, colubrid snake, blind snake, constrictor, elapid, elapid snake, sea snake, viper.

serpent (noun)	worm snake (noun)
limbless scaly elongate reptile; some are venomous	wormlike burrowing snake of warm regions having vestigial eyes
an obsolete bass cornet; resembles a snake	small reddish wormlike snake of eastern United States
a firework that moves in serpentine manner when ignited