asteroid

Word family

• asteroidal
  adjectiveC2

Synonym discussion

Sense: noun/1

These words all name objects in or from space, but they refer to different things. An asteroid is a rocky body that orbits the sun, mostly between Mars and Jupiter; 'minor planet' is the formal scientific label for the same object. A comet is icier and grows a long bright tail when it nears the sun, so its visual signature is unmistakable. A meteor is not an object but an event — the streak of light you see when a small piece of space rock burns up in Earth's atmosphere. If a fragment survives that fall and reaches the ground, scientists then call it a meteorite. So in everyday writing, say 'an asteroid passed close to Earth', 'a comet appeared with a glowing tail', 'a meteor lit up the night sky', and 'a meteorite was found in the desert.'

Common collocations

Etymology

The word entered English in 1802, when astronomer William Herschel coined it for the small starlike points of light he saw moving among the planets. He built it from the Greek root 'aster' (star) plus the ending '-oid' (meaning 'looking like'), so the literal sense is 'star-like'. Through a telescope these tiny rocks appeared as dots no bigger than stars, even though they are actually small rocky worlds orbiting the sun. The much rarer adjective use, meaning 'star-shaped', stays closer to the original Greek meaning and survives in technical fields like biology and pathology.