equator

noun

equa·​tor i-ˈkwā-tər 

ˈē-ˌkwā-

1

: the great circle of the celestial sphere whose plane is perpendicular to the axis of the earth

2

: a great circle of the earth or a celestial body that is everywhere equally distant from the two poles and divides the surface into the northern and southern hemispheres

3

a

: a circle or circular band dividing the surface of a body into two usually equal and symmetrical parts

b

: equatorial plane

the equator of a dividing cell

4

: great circle

Examples of equator in a Sentence

Recent Examples on the Web

Sweep a 6-inch telescope across the line separating night from dark — known as the terminator — slightly above the lunar equator to find the Montes Apennines mountain range curving from the shadowed to the sunlit side of the Earth's satellite. —Anthony Wood, Space.com, 10 Mar. 2026

The projection of Earth’s equator delineates the celestial equator, and the poles project onto the north and south celestial poles. —Vahe Peroomian, The Conversation, 5 Mar. 2026

That's the date of the vernal equinox, when the sun will shine directly over Earth's equator, creating roughly 12 hours of day and 12 hours of night across the world. —John Tufts, IndyStar, 5 Mar. 2026

However, the Apollo missions ventured to similar sites near the lunar equator on the moon’s near side, where the terrain was flat and astronauts could remain within reach of communication satellites. —Ashley Strickland, CNN Money, 21 Feb. 2026

Word History

Etymology

Middle English, from Medieval Latin aequator, literally, equalizer, from Latin aequare

First Known Use

14th century, in the meaning defined at sense 1

Phrases Containing equator

• celestial equator
• magnetic equator
• the equator

Rhymes for equator

• coater
• creator
• curator
• debater
• deflator
• dictator
• dilator
• locator
• mutator
• piscator
• pronator
• relator

Kids Definition

equator

noun

equa·​tor i-ˈkwāt-ər 

ˈē-ˌkwāt-

: an imaginary circle around the earth everywhere equally distant from the north pole and the south pole

Medical Definition

equator

noun

equa·​tor i-ˈkwāt-ər  ˈē-ˌ 

1

: a circle or circular band dividing the surface of a body into two usually equal and symmetrical parts especially at the place of greatest width

the equator of the lens of the eye

2

: equatorial plane