The word “planet” ultimately comes from ancient Greek and originally meant “wanderer.”

Where the word comes from

  • English “planet” comes from Middle English planete and Old French planete.
  • Those go back to Latin planeta (also planetes).
  • Latin borrowed the word from Ancient Greek πλανήτης (planētēs), an expression shortened from ἀστέρες πλανῆται (asteres planētai), meaning “wandering stars.”

What it originally meant

  • For the Greeks, “planētēs” described the bright points of light that wandered across the sky compared with the fixed background stars.
  • These “wanderers” were the Sun, Moon, Mercury, Venus, Mars, Jupiter, and Saturn as seen from Earth.
  • The idea was not about worlds like Earth at first, but about visible lights whose paths changed night after night.

How the meaning changed

  • In early astronomy, a “planet” was any of those wandering lights, excluding Earth.
  • By the 17th century, as heliocentric models took hold, “planet” shifted toward the modern sense: a world orbiting a star.
  • Today, the word still carries that old “wandering” root, even though we now define planets by their orbits and physical properties, not just by how they look in the sky.

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