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

nature / spontaneity

natural / spontaneous

naturally / spontaneously / rarely / coincidentally

(elementary mathematics) word problem

experimental results

school grammar / (specifically) Japanese school grammar, based on Shinkichi Hashimoto's work and now universally employed in Japanese schools and dictionaries.