monster vs behemoth

monster and behemoth both are nouns.

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

As nouns, monster and behemoth are synonyms defined as:

Other synonyms of monster include colossus, giant, goliath.

monster (noun)	behemoth (noun)
(medicine) a grossly malformed and usually nonviable fetus	someone that is abnormally large and powerful
a cruel wicked and inhuman person	a person of exceptional importance and reputation
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