forcefulness vs vigor

forcefulness and vigor both are nouns.

Word	Noun	Adjective	Verb	Adverb
forcefulness	Yes	No	No	No
vigor	Yes	No	No	No

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

Other hyponyms of forcefulness include brunt, impulse, momentum, energy, vigour, zip.

forcefulness (noun)	vigor (noun)
physical energy or intensity	active strength of body or mind
	an imaginative lively style (especially style of writing)
	forceful exertion