An astronaut is a person trained, equipped, and deployed by a human spaceflight program to serve as a commander or crew member aboard a spacecraft. Although generally reserved for professional space travelers, the terms are sometimes applied to anyone who travels into space, including scientists, politicians, journalists and tourists.
"Astronaut" technically applies to all human space travelers regardless of nationality or allegiance; however, astronauts fielded by Russia or the Soviet Union are typically known instead as cosmonauts in order to distinguish them from American or otherwise NATO-oriented space travellers. Comparatively recent developments in manned spaceflight made by China have led to the rise of the term taikonaut, although its use is somewhat informal and its origin is unclear. In Mainland China, the People's Liberation Army Astronaut Corps astronauts and their foreign counterparts are all officially called hángtiānyuán and "astronauts" in English.
Until 2002, astronauts were sponsored and trained exclusively by governments, either by the military or by civilian space agencies.