水洗
すいせん · suisen · JLPT N3 · noun
flushing
🚽💧 水洗 = water + wash, so a water-washed (flush) toilet
水 (sui) means water and 洗 (sen) means wash. Together they mean washing something away with water. The word is used mostly for flush toilets: 水洗トイレ (suisen toire).
水 — pictograph of flowing water
水 is a pictograph depicting a stream of flowing water, with the central line representing the main current and the side strokes showing splashing droplets or ripples. In oracle bone script it was drawn even more clearly as a wavy vertical line with branches. It retains its original meaning of 'water' and also serves as a radical, often appearing in the compressed form 氵.
洗 — water radical 氵 + 先 (xiān)
A semantic-phonetic compound. The water radical 氵 indicates the meaning (washing with water), while 先 supplies the sound, originally close to xiǎn/xǐ. The character has long meant 'to wash' or 'rinse,' and by extension 'to cleanse' or 'wash away.'