equator

American  

[ih-kwey-ter] / ɪˈkweɪ tər /

noun

1. 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.

2. the great circle of the earth that is equidistant from the North Pole and South Pole.

3. a circle separating a surface into two congruent parts.

4. celestial equator.

---

equator British  

/ ɪˈkweɪtə /

noun

1. the great circle of the earth with a latitude of 0°, lying equidistant from the poles; dividing the N and S hemispheres

2. a circle dividing a sphere or other surface into two equal symmetrical parts

3. See magnetic equator

4. astronomy See celestial equator

---

equator Scientific  

/ ĭ-kwā′tər /

1. 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.

2. A similar circle on the surface of any celestial body.

3. The celestial equator.

---

equator Cultural  

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

---

Etymology

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

Explanation

An equator is a circle that divides the surface of an object into two equal halves. If you're freezing up there in Iceland, get yourself on down closer to the earth's equator, where it's nice and warm. An equator is an invisible line that divides a globe into two parts, north and south. To remember equator, recall the root "equa" from the Latin word aequus, meaning "equal." An equator makes things "equal." If you drew a line that divided a globe into two parts that were not equal, the line couldn't be called an equator. If you live at the North Pole and you're buddy lives at the South, meet halfway, somewhere along the equator—perhaps in Brazil, for Carnaval.

Example Sentences

A dusk/dawn SSO orbit follows the earth’s rotation, passing near the poles, crossing the equator about the same time each day.

From The Wall Street Journal • May 12, 2026

High temperatures are nothing new in the west African nation, perched just above the equator.

From Barron's • Apr. 8, 2026

Kourou's position close to the equator on the South American continent has some launch advantages, but European-built rockets must be shipped thousands of kilometres then reassembled, adding to logistical challenges.

From BBC • Feb. 23, 2026

Researchers from Rice University used a climate model modified for Mars to explore whether lakes could have survived in places such as Gale Crater near the planet's equator.

From Science Daily • Feb. 6, 2026

It's equivalent to driving three-fourths of the way around the world at the equator.

From "100 Sideways Miles" by Andrew Smith

Related Words

• ring
• sphere