(history) a 律令 (ritsuryō) position in the 後宮 (Kōkyū, “Seraglio”) that manages water and ice

(history) a 律令 (ritsuryō) position in the 後宮 (Kōkyū, “Seraglio”) that manages water and ice / Alternative spelling of 主水司

the Wei River

spirogyra

(chemistry) hydration (incorporation of water molecules into another compound)

subterranean river / water from a subterranean river

(formal) [I, we] wish you a happy new year (literally meet a good year)

excuse me; may I come in?

the student has surpassed his or her teacher

(idiomatic) "a fish who's found water" → In one's element, a duck to water.