pixie vs sandman

pixie and sandman both are nouns.

Word	Noun	Adjective	Verb	Adverb
pixie	Yes	No	No	No
sandman	Yes	No	No	No

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

pixie: (folklore) fairies that are somewhat mischievous
sandman: an elf in fairy stories who sprinkles sand in children's eyes to make them sleepy

Other hyponyms of pixie include leprechaun.

pixie (noun)	sandman (noun)
(folklore) fairies that are somewhat mischievous	an elf in fairy stories who sprinkles sand in children's eyes to make them sleepy
creeping evergreen shrub having narrow overlapping leaves and early white star-shaped flowers; of the pine barrens of New Jersey and the Carolinas