[per-uh-hee-lee-uhn, -heel-yuhn]
noun, plural perihelia [per-uh-hee-lee-uh, -heel-yuh] . Astronomy.
the point in the orbit of a planet or comet at which it is nearest to the sun.
Compare aphelion.

1660–70; < Greek peri- peri- + hḗli(os) sun + -on neuter noun suffix, on the model of perigee; earlier in the Neo-Latin form perihelium

perihelial, perihelian, adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
perihelion (ˌpɛrɪˈhiːlɪən)
n , pl -lia
Compare aphelion the point in its orbit when a planet or comet is nearest the sun
[C17: from New Latin perihēlium, from peri- + Greek hēlios sun]

Collins English Dictionary - Complete & Unabridged 10th Edition
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Word Origin & History

"point at which a celestial body is nearest the Sun," 1690, coined in Mod.L. (perihelium) by Kepler (1596) from Gk. peri "near" + helios "sun" (see sol), and subsequently re-Grecianized.
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Science Dictionary
perihelion  [%PREMIUM_LINK%]     (pěr'ə-hē'lē-ən)  Pronunciation Key 

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The point at which an orbiting object, such as a planet or a comet, is closest to the Sun. Compare aphelion, perigee.

The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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