宇

Phono-semantic compound:

宀 (roof, house) — semantic, indicating a dwelling or shelter.

于 (particle 우) — phonetic element.

Originally denoted the structure of a house roof, then broadened in meaning to encompass the idea of “covering space.”

Semantic range:

- house, building, roof;

- eaves, overhang;

- by extension: spatial expanse, the universe (esp. paired with 宙 to mean “cosmos”).

우주 (宇宙) — the universe

제우 (帝宇) — imperial palace, royal residence

사우 (四宇) — the four directions, the whole world

천지우 (天地宇) — heaven and earth, the cosmic structure

In Huainanzi (회남자), 宇 is defined as:

四方上下 謂之宇 — “The four directions and above and below, this is called 宇.”

This reflects 宇 as the spatial dimension (space, extension in all directions), while 宙 represents the temporal dimension (time, past to present). Together 宇宙 signifies the complete cosmos of space-time.