fundamental, basic

understanding, comprehension / appreciation

concept, general idea

basis, foundation / (martial arts) kihon

understand, comprehend / appreciate

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

mechanics (a branch of physics)

a target, a mark, a bullseye / an objective, an object (of doing something)