uchu

Uchū (宇宙) is a Japanese noun meaning space or the cosmos—the universe. In Hepburn romanization it is written uchū, with a long u; in less formal or older texts it is often rendered as uchuu or uchu. The two kanji 宇 and 宙 form a compound that denotes the vast expanse beyond Earth.

The term appears in everyday language and scientific vocabulary. Common phrases include 宇宙飛行士 (astronaut), 宇宙開発 (space development or exploration), and 宇宙空間 (outer space). The word also occurs in compounds describing astronomical and cosmological concepts, such as 宇宙論 (cosmology). In general, uchū denotes both the physical cosmos and the broader concept of the universe.

In Japanese culture, uchū is a frequent motif in science fiction, educational media, literature, and film, serving to evoke vastness, mystery, and exploration. The term also appears in names of organizations, projects, or products, where it conveys a connection to space or futuristic themes. Despite its wide use, the core meaning remains space and the universe, rather than any particular celestial body.

Related topics include astronomy, cosmology, and space exploration.