ecliptic

American  

[ih-klip-tik] / ɪˈklɪp tɪk /

noun

1. Astronomy.

   1. the great circle formed by the intersection of the plane of the earth's orbit with the celestial sphere; the apparent annual path of the sun in the heavens.

   2. an analogous great circle on a terrestrial globe.

2. Astrology. the great circle of the ecliptic, along which are located the 12 houses and signs of the zodiac.

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adjective

1. pertaining to an eclipse.

2. pertaining to the ecliptic.

ecliptic British  

/ ɪˈklɪptɪk /

noun

1. astronomy

   1. the great circle on the celestial sphere representing the apparent annual path of the sun relative to the stars. It is inclined at 23.45° to the celestial equator. The poles of the ecliptic lie on the celestial sphere due north and south of the plane of the ecliptic

   2. ( as modifier )

      the ecliptic plane

2. an equivalent great circle, opposite points of which pass through the Tropics of Cancer and Capricorn, on the terrestrial globe

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adjective

1. of or relating to an eclipse

ecliptic Scientific  

/ ĭ-klĭp′tĭk /

1. The great circle on the celestial sphere that represents the Sun's apparent path among the background stars in one year. The northernmost point this path reaches on the celestial sphere is the Tropic of Cancer, its southernmost point is the Tropic of Capricorn, and it crosses the celestial equator at the points of vernal and autumnal equinox.

2. ◆ The plane of the ecliptic is the imaginary plane that intersects the celestial sphere along the ecliptic, and the north and south ecliptic poles are the points where a perpendicular line through the middle of this plane intersect the sphere. The plane of the ecliptic corresponds to the plane in which the Earth orbits the Sun. If the Earth's axis were not tilted, the ecliptic would be identical to the celestial equator and the ecliptic poles identical to the celestial poles. In this case, the Sun's path would not move northward or southward from the equator during the year. As it is, the plane of the celestial equator is tilted 23.45° to the plane of the ecliptic, corresponding to the tilt of the Earth's axis with respect to its orbital plane, giving the Sun its apparent northward and southward movement among the background stars.

3. See illustration at celestial sphere

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Other Word Forms

• ecliptically adverb
• nonecliptic adjective
• nonecliptical adjective
• nonecliptically adverb
• unecliptic adjective
• unecliptical adjective
• unecliptically adverb

Etymology

Origin of ecliptic

1350–1400; Middle English < Medieval Latin eclīptica, feminine of eclīpticus < Greek ekleiptikós, equivalent to ekleíp ( ein ) ( see eclipse) + -tikos -tic

Explanation

Astronomers use the noun ecliptic to describe the sun's path as it's seen from the Earth. You're most likely to come across the word ecliptic in an astronomy class, since it's a technical term for the apparent path of the sun through the stars over the course of a year. It's not possible to see the ecliptic, since the rotation of the Earth complicates our perspective of the sun's movement, but astronomers have long described and drawn it. It's called an ecliptic because eclipses only happen when the moon crosses it.

Example Sentences

More recently, the European Space Agency's Solar Orbiter has been gradually moving out of the ecliptic plane and is expected to reach latitudes of around 34° in a few years.

From Science Daily • Oct. 14, 2025

All the planets orbit roughly along the same plane, known as an ecliptic plane, or arc across the sky if you are viewing it edge-on, according to NASA.

From Los Angeles Times • Feb. 26, 2025

Conjunctions occur frequently in our solar system because "the planets orbit around the Sun in approximately the same plane - the ecliptic plane - and thus trace similar paths across our sky", according to Nasa.

From BBC • Feb. 28, 2023

And whereas Ptolemy based his coordinate system on the ecliptic, Hipparchus used the celestial equator, a system more common in modern star maps.

From Scientific American • Oct. 20, 2022

The planet has a few degrees of tilt to the plane of the ecliptic, not enough to make an appreciable seasonal difference in low latitudes.

From "The Left Hand of Darkness" by Ursula K. Le Guin

Related Words

• ring
• sphere