pupil vs student

pupil and student both are nouns.

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

As nouns, pupil and student are synonyms defined as:

pupil and student: a learner who is enrolled in an educational institution

Other synonyms of pupil include educatee.

pupil (noun)	student (noun)
the contractile aperture in the center of the iris of the eye; resembles a large black dot	a learner who is enrolled in an educational institution
a learner who is enrolled in an educational institution	someone (especially a child) who learns (as from a teacher) or takes up knowledge or beliefs
a young person attending school (up through senior high school)