宇宙
yǔzhòu · HSK 7
world
🌌 宇 = roof/space + 宙 = time; together the cosmos = all space and time
宇 is the spatial reach of the universe and 宙 is its span across time, so 宇宙 literally pairs space with time to mean the whole cosmos. Both share the 宀 roof radical, marking them as the great shelter over everything that exists.
宙 — roof 宀 + 由 (phonetic)
宙 is a semantic-phonetic compound: the roof radical 宀 suggests space or dwelling, while 由 supplies the sound. Originally referring to the ridgepole of a roof, it came to mean 'time' or 'eternity,' and pairs with 宇 (space) in 宇宙 'universe.'