luxuria vs mortal sin

luxuria and mortal sin both are nouns.

Word	Noun	Adjective	Verb	Adverb
luxuria	Yes	No	No	No
mortal sin	Yes	No	No	No

As nouns, mortal sin is a hypernym of luxuria; that is, mortal sin is a word with a broader meaning than luxuria:

luxuria: self-indulgent sexual desire (personified as one of the deadly sins)
mortal sin: an unpardonable sin entailing a total loss of grace

Other hypernyms of luxuria include deadly sin.

luxuria (noun)	mortal sin (noun)
self-indulgent sexual desire (personified as one of the deadly sins)	an unpardonable sin entailing a total loss of grace