sinning vs mortal sin

sinning and mortal sin both are nouns.

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

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

sinning: an act that is regarded by theologians as a transgression of God's will
mortal sin: an unpardonable sin entailing a total loss of grace

Other hyponyms of sinning include fall, actual sin, original sin, deadly sin, venial sin.

sinning (noun)	mortal sin (noun)
an act that is regarded by theologians as a transgression of God's will	an unpardonable sin entailing a total loss of grace

sinning (adjective)	mortal sin (adjective)
transgressing a moral or divine law