languor vs listlessness

languor and listlessness both are nouns.

Word	Noun	Adjective	Verb	Adverb
languor	Yes	No	No	No
listlessness	Yes	No	No	No

As nouns, languor and listlessness are synonyms defined as:

Other synonyms of languor include lassitude.

languor (noun)	listlessness (noun)
inactivity; showing an unusual lack of energy	inactivity resulting from lethargy and lack of vigor or energy
a relaxed comfortable feeling	a feeling of lack of interest or energy
a feeling of lack of interest or energy
oppressively still air