How to say "planet" in Japanese

• 惑星わくせいJLPT N1approx.Common
  nounThe dedicated word for a planet as an astronomical body; use it in scientific, educational, or science-fiction contexts, such as discussing the planets of the solar system or planetary exploration.
  他ほかの惑星わくせいには生命せいめいが存在そんざいするのですか。↗

  Is there life on other planets?
• 星ほしJLPT N4approx.Common
  nounCovers 'planet' when talking about the night sky, usually planets other than Earth; it is really the general word for a star or heavenly body, so use 惑星 when you need the astronomical term.
  昨夜さくや、屋上おくじょうから星ほしを観察かんさつした。↗

  Last night, we watched the stars from the rooftop.

Use 惑星 when you mean a planet as an astronomical object; use 星 for planets spoken of as lights in the night sky, remembering that in its planet sense it usually excludes Earth.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• 惑星わくせいplanet
• 星ほしstar (usu. excluding the Sun)
• プラネットplanet
• 遊星ゆうせいplanet