灰尘
huī chén · HSK 7
dust
灰 = ash/grey + 尘 = dust; and 尘 itself = 小 (small) + 土 (earth) = tiny bits of earth
灰 means ash or grey, 尘 means dust. The character 尘 stacks 小 (small) over 土 (earth) — literally small earth, the fine specks that settle as dust. Together: grey, ashy dust.
灰 — hand 又 (ナ) + fire 火
灰 originally depicted a hand (ナ, simplified from 又) holding or reaching into fire 火, representing the cooled ashes one can safely pick up after a flame dies. From this concrete sense of 'ashes,' the meaning extended to the color gray and figuratively to discouragement, as in 灰心.