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Glite Dictionary
semidiameter

semidiameter

9.6
Half the visible width of an object in the sky as seen from Earth
  • noun
  • /ˌsɛmɪˈdaɪəmɪtər/
  • Specialized
translation icon : semidiametro
  • The Moon's semidiameter changes slightly as its distance from Earth varies.

Examples

  • Astronomers calculate the Sun's semidiameter to help predict solar eclipses.

  • The apparent semidiameter of Mars was measured during the observation.

  • The semidiameter of the Moon is about 1,737 kilometers.

  • Did you know the semidiameter of the Sun is approximately 696,340 kilometers?

  • Astronomers calculate the Sun's semidiameter to help predict solar eclipses.

  • The Moon's semidiameter changes slightly as its distance from Earth varies.

  • Did you know the semidiameter of the Sun is approximately 696,340 kilometers?

Synonyms

radius
vssemidiameter
  • Specialized
10 3.2

A straight line from the center of a circle or sphere to its edge

refers to the apparent distance seen from Earth rather than the true geometric length

Surface Forms

semidiameter singular
semidiameters plural

Morphology

semidiameter = diameter (semi-transparent) = semi + diameter

The word clearly means 'half of a diameter', but its use as a technical astronomical term is more specialized than the basic parts alone.

Etymology

Semidiameter comes from semi- meaning 'half' and diameter meaning 'measure across', and a diameter is the line that goes across a circle. So a semidiameter is 'half' of that line, which is why the word is used for the apparent radius of the Sun, Moon, or a planet as seen from Earth.