What does cosmonaut mean?
A cosmonaut is a person who has been trained to travel into space, the term being applied specifically to space travellers of the Russian or former Soviet space programmes. The word entered English during the early years of human spaceflight, at a time when the United States and the Soviet Union were competing head-to-head in the Space Race: American space travellers were called astronauts, while Soviet ones were called cosmonauts. Both words derive ultimately from Greek roots — 'cosmo-' meaning universe or order, and 'naut' meaning sailor — so both literally suggest a 'sailor of the cosmos'. The distinction remains conventional rather than technical: cosmonauts perform essentially the same role as astronauts, flying spacecraft, living on space stations, and carrying out scientific work in orbit. The word is neutral in tone and appears frequently in historical accounts of Soviet achievements such as Yuri Gagarin's pioneering flight and Valentina Tereshkova's mission as the first woman in space.
nounAn astronaut, specifically one employed by or representing the Russian or former Soviet space programme.
- A person trained to travel in a spacecraft, specifically one from the Russian or Soviet space programme.
"Yuri Gagarin became the first cosmonaut when he orbited the Earth aboard Vostok 1 in 1961."
"The cosmonaut spent six months aboard the Mir space station conducting scientific experiments."
"Valentina Tereshkova made history as the first woman cosmonaut, orbiting the Earth forty-eight times in 1963."
Regular plural; simply add -s.
"Two cosmonauts conducted a spacewalk outside the station to repair a damaged solar panel."
While Americans trained astronauts, the Soviets launched cosmonauts — same job title, two rival words born of the Space Race.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of cosmonaut
Cosmonaut was coined in Russian as kosmonavt (космонавт) in the late 1950s or early 1960s, formed from the Greek-derived elements kosmos ('universe', literally 'order') and nautes ('sailor'). It was adopted directly into English as the official term for Soviet space travellers, mirroring 'astronaut', which comes from the Greek roots astron ('star') and nautes. The parallel construction makes the two words true siblings, differing only in whether they sail among the stars or across the cosmos.
How cosmonaut is actually used
Neutral in register. The term carries no negative connotation; it is the standard word for Russian and former Soviet space travellers, just as 'astronaut' is for American and many other national space agency personnel. Some other countries' agencies use their own equivalents (e.g. Chinese taikonauts).
Easily confused with cosmonaut
Astronaut is the general English term for a space traveller and is used especially for those in the American or international programmes, while cosmonaut refers specifically to a Russian or Soviet space traveller.