sadness vs lugubriousness

sadness and lugubriousness both are nouns.

Word	Noun	Adjective	Verb	Adverb
sadness	Yes	No	No	No
lugubriousness	Yes	No	No	No

As nouns, sadness and lugubriousness are synonyms defined as:

sadness and lugubriousness: the quality of excessive mournfulness and uncheerfulness

Other synonyms of sadness include gloominess.

sadness (noun)	lugubriousness (noun)
the quality of excessive mournfulness and uncheerfulness	the quality of excessive mournfulness and uncheerfulness
emotions experienced when not in a state of well-being
the state of being sad