What does comet mean?
A comet is a small celestial body composed largely of ice, dust, and rocky material that orbits the Sun, typically on an elongated elliptical path. When a comet approaches the Sun, solar heating causes its ices to vaporize, producing a diffuse glowing envelope called a coma and often one or more tails — one of gas and one of dust — that can stretch millions of kilometres and point away from the Sun regardless of the comet's direction of travel. Comets range in size from a few hundred metres to tens of kilometres across their nuclei. Some, known as short-period comets such as Halley's Comet, return at predictable intervals, while others arrive from the distant outer solar system on journeys spanning thousands or millions of years. Historically regarded with awe or dread as omens, comets are now understood as pristine remnants from the formation of the solar system, offering scientists valuable clues about its early composition and origins.
nounA celestial body consisting of a nucleus of ice, dust, and rock that, when passing close to the Sun, develops a glowing coma and often one or more tails of gas and dust.
- A small solar system body of ice and dust that develops a glowing coma and often a tail when heated by the Sun near perihelion.
"The comet streaked across the night sky, its luminous tail visible even to the naked eye."
"Halley's Comet returns to the inner solar system roughly every 76 years."
"Astronomers tracked the newly discovered comet for months as it brightened on approach to the Sun."
Standard regular plural; used in both scientific and general contexts.
"Several bright comets were recorded by astronomers during the seventeenth century."
The word 'comet' comes from the Greek for 'long-haired star' — ancient Greeks literally saw these icy wanderers as stars wearing flowing locks of light.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of comet
The word 'comet' derives ultimately from the Greek adjective komētēs, meaning 'long-haired' or 'wearing long hair', which was applied to these objects because of their streaming tails; the full Greek phrase was aster komētēs, 'long-haired star'. It passed into Latin as comēta before entering English in the Middle English period via Old French comète. The same Greek root gave rise to the modern astronomical terms 'coma' and 'cometary', both used to describe the fuzzy, hair-like appearance of a comet's head.
Related word forms
How comet is actually used
Used almost exclusively in astronomy and popular science writing; figurative uses are rare. Plural is 'comets'.
Easily confused with comet
A 'comment' is a remark or written observation, while a 'comet' is an icy celestial body orbiting the Sun.