total darkness vs lightlessness

total darkness and lightlessness both are nouns.

Word	Noun	Adjective	Verb	Adverb
total darkness	Yes	No	No	No
lightlessness	Yes	No	No	No

As nouns, total darkness and lightlessness are synonyms defined as:

Other synonyms of total darkness include black, blackness, pitch blackness.

total darkness (noun)	lightlessness (noun)
total absence of light	total absence of light