base, basis, foundation, ground, root / (construction, architecture) foundation

to study / to learn

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

fundamental, basic

(mathematics) pure mathematics

applied mathematics

mathematician