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

Kyūjitai form of 潮汐学

(sciences) tidology

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

a sea, an ocean / a lake / (figuratively) an object covering over a large area, as in 血の海 (chi no umi, “pool of blood”) or 火の海 (hi no umi, “sea of fire”)