What does asteroid mean?
An asteroid is a relatively small, rocky or metallic body that orbits the Sun, most famously concentrated in the asteroid belt between the orbits of Mars and Jupiter. Ranging from tiny boulders to dwarf-planet-sized worlds like Ceres, asteroids are leftovers from the formation of the solar system some 4.6 billion years ago, which makes them scientifically valuable as pristine records of its early history. In everyday usage the word appears frequently in news coverage of space missions, impact risks, and planetary science, with common pairings such as 'asteroid belt', 'near-Earth asteroid', and 'asteroid impact'. Astronomers sometimes favor the more formal term 'minor planet', reserving 'asteroid' for bodies that are neither comets nor planets. It should not be confused with a meteorite, which is a fragment that has already landed on Earth. The word derives from Greek roots meaning 'star-like', reflecting how these objects appeared to early telescopic observers.
nounA small rocky body orbiting the Sun, especially one found between the orbits of Mars and Jupiter; also called a minor planet. More broadly, any of numerous small celestial bodies composed of rock and metal that are larger than meteoroids but much smaller than planets.
- A small rocky or metallic body orbiting the Sun, especially one located in the asteroid belt between Mars and Jupiter.
- Any similar minor planet or small natural rocky body orbiting another star or the Sun outside the main belt.
"The spacecraft spent two years orbiting a distant asteroid to collect samples from its surface."
"Ceres is the largest object in the asteroid belt between Mars and Jupiter."
"Scientists monitor near-Earth asteroids closely to assess any potential impact risk."
Regular English plural; no irregular forms exist.
"Thousands of asteroids have been catalogued by modern surveys."
William Herschel coined 'asteroid' in 1802 because these bodies looked like stars — even though they're really more like flying mountains.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of asteroid
The word 'asteroid' comes from the Greek 'astēroeidēs', formed from 'astēr' (star) plus '-eides' (having the form of), so it literally means 'star-shaped' or 'star-like'. It was coined in English by the astronomer William Herschel in 1802, shortly after the discovery of the first objects of this kind between Mars and Jupiter, because they appeared through telescopes merely as points of light resembling stars rather than disks like planets. The root 'astēr' also underlies a wide family of English words including astronomy, astrology, astral, asterisk, and aster.
How asteroid is actually used
Astronomers increasingly prefer the term 'minor planet' for formal classification, since 'asteroid' originally referred specifically to star-like points of light. The plural is regular (asteroids). The word carries no strong register constraints and appears freely in both scientific writing and popular journalism.
Easily confused with asteroid
An asteroid is a rocky body in space; a meteorite is the fragment that actually lands on Earth's surface after surviving passage through the atmosphere.
An asteroid is made mostly of rock and metal, while a comet is largely ice and dust and develops a glowing tail when heated by the Sun.