heaviness vs burdensomeness

heaviness and burdensomeness both are nouns.

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

As nouns, heaviness and burdensomeness are synonyms defined as:

Other synonyms of heaviness include onerousness, oppressiveness.

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