The kanji 宙 generally refers to "space," "sky," or "the universe." It embodies the idea of a vast, boundless expanse, encompassing the heavens and everything within it. It can also imply a sense of emptiness or an interval of time.

・On-yomi (音読み): チュウ (chuu) ・Kun-yomi (訓読み): None, or rarely used as a standalone kun-yomi.

⚫︎ 宇宙 (uchuu) Translation: Universe, cosmos ⚫︎ 空中 (kuuchuu) Translation: In the air, airborne ⚫︎ 宙返り (chugaeri) Translation: Somersault

The kanji 宙 is a pictophonetic compound. The character is composed of the radical 宀 (うかんむり – ukanmuri), which means "roof" or "house," and the phonetic component 由 (yuu), meaning "reason" or "cause." Initially, 宀 might have been suggestive of a shelter and 由 possibly representing something enclosed. Over time, the meaning shifted towards the broad, encompassing "space" or "sky" due to 由 being used phonetically. Thus, the character combined an element of a covered space with the phonetic sound and the broadened meaning, evolving to signify the vastness and boundlessness of the sky and space.