Definition of sidereal day in English:

sidereal day

Syllabification: si·de·re·al day

noun

Astronomy
  • The time between two consecutive transits of the First Point of Aries. It represents the time taken by the earth to rotate on its axis relative to the stars, and is almost four minutes shorter than the solar day because of the earth’s orbital motion.
    More example sentences
    • These sessions were performed during two consecutive days but delayed by 4 minutes per day, since the satellite sky distribution is repeated with a period close to a sidereal day.
    • Over the past few sidereal days more radio signals from an as-yet-unidentified source have been detected.
    • I understand the concepts of the sidereal day, and am happy with my intuitive notions of the Earth's rotation and movement relative to the sun and the solar system.

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Word of the day milord
Pronunciation: mɪˈlɔːd
noun
used to address an English nobleman