castaway vs leper

castaway and leper both are nouns.

Word	Noun	Adjective	Verb	Adverb
castaway	Yes	No	No	No
leper	Yes	No	No	No

As nouns, leper is a hyponym of castaway; that is, leper is a word with a more specific, narrower meaning than castaway:

Other hyponyms of castaway include heretic, misbeliever, religious outcast, Harijan, untouchable.

castaway (noun)	leper (noun)
a shipwrecked person	a pariah who is avoided by others
a person who is rejected (from society or home)	a person afflicted with leprosy