serpent vs elapid snake

serpent and elapid snake both are nouns.

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

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

serpent: limbless scaly elongate reptile; some are venomous
elapid snake: any of numerous venomous fanged snakes of warmer parts of both hemispheres

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

serpent (noun)	elapid snake (noun)
limbless scaly elongate reptile; some are venomous	any of numerous venomous fanged snakes of warmer parts of both hemispheres
an obsolete bass cornet; resembles a snake
a firework that moves in serpentine manner when ignited