to teach

teacher

pupil, educatee, student (especially in junior high schools (中学校) or high schools (高校) in Japan)

mathematics (field of study)

he / distal demonstrative, something far off removed from both speaker and listener: that / boyfriend

distal demonstrative, something far off removed from both speaker and listener: that, yon / particularly, male personal third person pronoun: he / by extension from he: boyfriend

he; boyfriend

student council

(mathematics) discrete mathematics

applied mathematics