weightiness vs heft

weightiness and heft both are nouns.

Word	Noun	Adjective	Verb	Adverb
weightiness	Yes	No	No	No
heft	Yes	No	Yes	No

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

Other hyponyms of weightiness include heftiness, massiveness, ponderosity, ponderousness, preponderance.

weightiness (noun)	heft (noun)
the property of being comparatively great in weight	the property of being large in mass
the relative importance granted to something

weightiness (verb)	heft (verb)
	lift or elevate
	test the weight of something by lifting it