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aphelion Syllabification: a·phe·li·on
Pronunciation: /əˈfēlēən/

Definition of aphelion in English:

noun (plural apheliaəˈfēlēə or aphelions)

The point in the orbit of a planet, asteroid, or comet at which it is furthest from the sun: Mars is at aphelion The opposite of perihelion.
More example sentences
  • This affects the climate because the influx of solar energy to our planet would then vary between perihelion and aphelion by a larger proportion than at present.
  • This is because at aphelion the planet is moving slowest, and consequently it is less likely to pass across the Sun during the critical window.
  • There are small cyclic variations in those apparent sizes because the Earth-Moon distance changes as the latter moves between perigee and apogee, and the Earth-Sun separation alters as the former moves between perihelion and aphelion.


Mid 17th century: alteration of modern Latin aphelium (by substitution of the Greek inflection -on), from Greek aph' hēlion 'from the sun'.

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