水星(すいせい)

すいせい
noun
Mercury
science
1. Mercury
The first and smallest planet in the Solar System, closest to the Sun. Named after the element water (水) in the Chinese five-element system.
水星(すいせい)は太陽(たいよう)に最(もっと)も近(ちか)い惑星(わくせい)だ。
Mercury is the planet closest to the Sun.
水星(すいせい)は肉眼(にくがん)では見(み)えにくい。
Mercury is hard to see with the naked eye.
水星(すいせい)の表面温度(ひょうめんおんど)は昼(ひる)と夜(よる)で大(おお)きく変(か)わる。
The surface temperature of Mercury varies greatly between day and night.

Watch out

Do not confuse with the homophone 彗星(すいせい) (comet). Both are read すいせい but written with different kanji and have completely different meanings.

Etymology

Part of the Chinese five-element planet naming system. Wednesday (水曜日(すいようび)) is associated with Mercury, paralleling Western tradition.

Common collocations

  • 水星(すいせい)の軌道(きどう) (Mercury's orbit)
  • 水星(すいせい)探査(たんさ) (Mercury exploration)
  • 水星(すいせい)の公転周期(こうてんしゅうき) (Mercury's orbital period)

Related Words

Homophone: 彗星(すいせい)
Related: 金星(きんせい) (Venus)
Related: 火星(かせい) (Mars)
Related: 木星(もくせい) (Jupiter (planet))
Related: 惑星(わくせい) (planet)
general
Added 2026.3.20 17:56 · Revised 2026.10.10 22:29
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