pupil vs boarder

pupil and boarder both are nouns.

Word	Noun	Adjective	Verb	Adverb
pupil	Yes	No	No	No
boarder	Yes	No	No	No

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

Other hyponyms of pupil include day boarder, latchkey child, schoolboy.

pupil (noun)	boarder (noun)
the contractile aperture in the center of the iris of the eye; resembles a large black dot	a tenant in someone's house
a learner who is enrolled in an educational institution	a pupil who lives at school during term time
a young person attending school (up through senior high school)	someone who forces their way aboard ship