anomaly vs monster

anomaly and monster both are nouns.

Word	Noun	Adjective	Verb	Adverb
anomaly	Yes	No	No	No
monster	Yes	No	No	No

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

Other hyponyms of anomaly include aberrant, behemoth, colossus, giant, goliath, Jekyll and Hyde.

anomaly (noun)	monster (noun)
(astronomy) position of a planet as defined by its angular distance from its perihelion (as observed from the sun)	(medicine) a grossly malformed and usually nonviable fetus
a person who is unusual	a cruel wicked and inhuman person
deviation from the normal or common order or form or rule	a person or animal that is markedly unusual or deformed
	an imaginary creature usually having various human and animal parts
	someone that is abnormally large and powerful