to explain / to preach, to persuade

physics (as an area of study)

basis, foundation / (martial arts) kihon

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

physics, the physical aspects of a phenomenon or a system

(geology, physics) geophysics

astrophysics

(physics) theoretical physics