heaviness vs heft

heaviness and heft both are nouns.

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

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

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

heaviness (noun)	heft (noun)
the property of being comparatively great in weight	the property of being large in mass
used of a line or mark
unwelcome burdensome difficulty
an oppressive quality that is laborious and solemn and lacks grace or fluency
persisting sadness

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