潮汐学: tidology

specialist; expert

一石二鳥: “one stone, two birds” → kill two birds with one stone: do one task and finish two or more goals

(sciences) tidology

Kyūjitai form of 潮汐学

change, fluctuation

change, fluctuate

speciality/specialty; subject of study; subject of expertise; area of interest; profession

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