the great circle on a sphere or heavenly body whose plane is perpendicular to the axis, equidistant everywhere from the two poles of the sphere or heavenly body.
the great circle of the earth that is equidistant from the North Pole and South Pole.
a circle separating a surface into two congruent parts.

Origin of equator

1350–1400; Middle English < Medieval Latin aequātor, Latin: equalizer (of day and night, as when the sun crosses the equator). See equate, -tor
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Related Words for equator

sphere, ring, hoop, arc, bend, disk, eye, orb, circle, wheel, circlet, curvature, band, arch, gyre, ringlet, curve, orbit, bow, loop

Examples from the Web for equator

Contemporary Examples of equator

Historical Examples of equator

  • Aunt Jane approached a degree nearer the equator, and said, gently, "I fear I do."


    Thomas Wentworth Higginson

  • I may almost say their temperature would be the same at the Equator as the Pole.

    The Field of Ice

    Jules Verne

  • And he tells you that the earth south of the Equator makes the inferior man.

    Slavery Ordained of God

    Rev. Fred A. Ross, D.D.

  • There is no distinction between the equator and the ecliptic.

  • If it did, the equator would be frozen in twenty-four hours!

British Dictionary definitions for equator



the great circle of the earth with a latitude of 0°, lying equidistant from the poles; dividing the N and S hemispheres
a circle dividing a sphere or other surface into two equal symmetrical parts
astronomy See celestial equator

Word Origin for equator

C14: from Medieval Latin (circulus) aequātor (diei et noctis) (circle) that equalizes (the day and night), from Latin aequāre to make equal
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for equator

late 14c., from Medieval Latin aequator diei et noctis "equalizer of day and night" (when the sun is on the celestial equator, twice annually, day and night are of equal length), agent noun from Latin aequare "make equal" (see equate). Sense of "celestial equator" is earliest, extension to "terrestrial line midway between the poles" first recorded in English 1610s.

Online Etymology Dictionary, © 2010 Douglas Harper

equator in Science



An imaginary line forming a great circle around the Earth's surface, equidistant from the poles and in a plane perpendicular to the Earth's axis of rotation. It divides the Earth into the Northern and Southern hemispheres and is the basis from which latitude is measured.
A similar circle on the surface of any celestial body.
The celestial equator.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

equator in Culture


An imaginary circle around the Earth, equidistant from the North Pole and South Pole.

The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.