na-adjective, noun
clear and bright; limpid; lucid
Literary word describing something transparently clear and luminous, such as water, air, light, or a state of mind. Often used in poetic or refined contexts.
澄明な湖の水面に月が映っていた。
The moon was reflected on the limpid surface of the lake.
彼の心は澄明で、一点の曇りもなかった。
His mind was clear and bright, without a single cloud.
Compound of 澄 (clear, limpid) and 明 (bright, light). The exact historical derivation is uncertain, but the combination naturally conveys clarity and luminosity.