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[hi-lahy-uh-kuh l]
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adjective Astronomy.
  1. pertaining to or occurring near the sun, especially applied to such risings and settings of a star as are most nearly coincident with those of the sun while yet visible.
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Also he·li·ac [hee-lee-ak] /ˈhi liˌæk/.

Origin of heliacal

1600–10; < Late Latin hēliac(us) (< Greek hēliakós; see heli-1, -ac) + -al1
Related formshe·li·a·cal·ly, adverb
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Related Words for heliacal

cosmic, stellar, empyreal, heliacal

Examples from the Web for heliacal

Historical Examples of heliacal

  • He must mean either the heliacal or achronical rising of that sign.

    Discourses on Satire and on Epic Poetry

    John Dryden

  • They also possessed lists of the fixed stars, and drew up tables of the times of their heliacal risings.

  • Swart star: the Dogstar, called swarthy because its heliacal rising in ancient times occurred soon after mid-summer.

  • This was based upon the heliacal rising of Sirius (Sothis) coincident with the beginning of the inundation.

  • Implying hereby the Heliacal ascent and Cosmical descent of those stars.

Word Origin and History for heliacal


"pertaining to the sun," c.1600, with -al (1) and Greek heliakos "of the sun," from helios "sun" (see sol). The heliacal year is reckoned from the heliacal rising of Sirius; thus it also is known as the canicular year.

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Online Etymology Dictionary, © 2010 Douglas Harper