| Meaning | A circular line on the surface of a sphere formed by intersecting it with a plane passing through the center. |
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| Narrower | celestial equator, equinoctial circle, equinoctial line, equinoctial | The great circle on the celestial sphere midway between the celestial poles |
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| ecliptic | The great circle representing the apparent annual path of the sun |
| equator | An imaginary line around the Earth forming the great circle that is equidistant from the north and south poles |
| horizon, celestial horizon | The great circle on the celestial sphere whose plane passes through the sensible horizon and the center of the Earth |
| hour circle | A great circle on the celestial sphere that passes through both celestial poles |
| meridian, line of longitude | An imaginary great circle on the surface of the earth passing through the north and south poles at right angles to the equator |
| vertical circle | A great circle on the celestial sphere passing through the zenith and perpendicular to the horizon |
| Broader | line | A spatial location defined by a real or imaginary unidimensional extent |
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