mortal sin vs sloth

mortal sin and sloth both are nouns.

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

As nouns, sloth is a hyponym of mortal sin; that is, sloth is a word with a more specific, narrower meaning than mortal sin:

mortal sin: an unpardonable sin entailing a total loss of grace
sloth: apathy and inactivity in the practice of virtue (personified as one of the deadly sins)

mortal sin (noun)	sloth (noun)
an unpardonable sin entailing a total loss of grace	apathy and inactivity in the practice of virtue (personified as one of the deadly sins)
	any of several slow-moving arboreal mammals of South America and Central America; they hang from branches back downward and feed on leaves and fruits
	a disinclination to work or exert yourself