colubrid snake vs serpent

colubrid snake and serpent both are nouns.

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

As nouns, serpent is a hypernym of colubrid snake; that is, serpent is a word with a broader meaning than colubrid snake:

colubrid snake: mostly harmless temperate-to-tropical terrestrial or arboreal or aquatic snakes
serpent: limbless scaly elongate reptile; some are venomous

Other hypernyms of colubrid snake include ophidian, snake.

colubrid snake (noun)	serpent (noun)
mostly harmless temperate-to-tropical terrestrial or arboreal or aquatic snakes	limbless scaly elongate reptile; some are venomous
	an obsolete bass cornet; resembles a snake
	a firework that moves in serpentine manner when ignited