omen vs prognostication

omen and prognostication both are nouns.

Word	Noun	Adjective	Verb	Adverb
omen	Yes	No	Yes	No
prognostication	Yes	No	No	No

As nouns, omen and prognostication are synonyms defined as:

Other synonyms of omen include portent, presage, prodigy, prognostic.

omen (noun)	prognostication (noun)
a sign of something about to happen	knowledge of the future (usually said to be obtained from a divine source)
	a statement made about the future
	a sign of something about to happen

omen (verb)	prognostication (verb)
indicate, as with a sign or an omen