乌云
wū yún · HSK 6
black cloud
🌑☁️ 乌云 = crow-black + cloud — dark as a crow's wing overhead
乌 means crow or black (crows are jet-black). 云 means cloud. Together they name the dark, threatening storm clouds that roll in before rain.
云 — top 一 + 厶 (swirling cloud shape)
Originally a pictograph of a swirling cloud, written 云 in oracle bones. Later 雨 (rain) was added on top to form 雲, clarifying the weather meaning. In simplified Chinese, 云 was restored as the standard form and also serves as a literary verb meaning 'to say'.