from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. The apparent radius of a celestial body when viewed as a disk from Earth.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. The apparent radius of a star etc, when viewed from Earth
  • n. radius, half of a diameter

from the GNU version of the Collaborative International Dictionary of English

  • n. Half of a diameter; a right line, or the length of a right line, drawn from the center of a circle, a sphere, or other curved figure, to its circumference or periphery; a radius.

from The Century Dictionary and Cyclopedia

  • n. One half the diameter: especially, in astronomy, one half the angular diameter of the sun, moon, or other object showing a disk; the radius.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. the apparent radius of a celestial body when viewed as a disc from the earth


semi- +‎ diameter (Wiktionary)



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