清い
きよい · kiyoi · JLPT N2 · i-adj
noble
💧 清 = water radical 氵 + 青 (clear blue): clear, pure, clean water
The 氵 water radical marks 清's watery core, and 青 adds the sense of clear blue. Clean spring water is 清水 (shimizu), the same idea behind 清い.
清 — water 氵 + 青 (azure/blue-green, phonetic)
清 is a semantic-phonetic compound. The water radical 氵 gives the meaning—originally clear, unmuddied water—while 青 (qīng, azure) supplies the sound and reinforces the image of pure blue-green water. The sense later broadened from 'clear water' to 'clear, pure, clean' in general.