WEBMar 26, 2024 · 太陰 ( taiin ): the moon. From Middle Chinese 太陰 (tʰɑiᴴ ʔˠiɪm, “the moon ”, literally “great dark, great yin ”). Compare 太陽 (taiyō, “the sun ”, literally “great light, great yang ”). The kan'on reading, so either a later borrowing or a later development within Japan.