sidereal

[sahy-deer-ee-uh l] /saɪˈdɪər i əl/
adjective, Astronomy
1.
determined by or from the stars:
sidereal time.
2.
of or pertaining to the stars.
Origin
1625-35; < Latin sīdere(us) of, belonging to the stars (sīder-, stem of sīdus star, constellation + -eus adj. suffix) + -al1
Related forms
sidereally, adverb
nonsidereal, adjective
unsidereal, adjective
British Dictionary definitions for sidereal

sidereal

/saɪˈdɪərɪəl/
adjective
1.
of, relating to, or involving the stars
2.
determined with reference to one or more stars: the sidereal day
Derived Forms
sidereally, adverb
Word Origin
C17: from Latin sīdereus, from sīdus a star, a constellation
Word Origin and History for sidereal
adj.

also siderial, 1630s, "star-like;" 1640s, "of or pertaining to the stars," earlier sideral (1590s), from French sidereal (16c.), from Latin sidereus "starry, astral, of the constellations," from sidus (genitive sideris) "star, group of stars, constellation," probably from PIE root *sweid- "to shine" (cf. Lithuanian svidus "shining, bright"). Sidereal time is measured by the apparent diurnal motion of the fixed stars. The sidereal day begins and ends with the passage of the vernal equinox over the meridian and is about four minutes shorter than the solar day, measured by the passage of the sun over the meridian.

sidereal in Science
sidereal
  (sī-dîr'ē-əl)   

  1. Relating to the stars or constellations.

  2. Measured with respect to the background of fixed stars instead of the Sun.