Equator (noun)

1. An imaginary great circle around the Earth, equidistant from the poles, dividing the Earth into northern and southern hemispheres.
2. An imaginary great circle around a celestial body, such as a planet, parallel to its axis of rotation and equidistant from its poles.

Origin:

Late latin aequator, from latin aequare "make equal", from aequus "equal".

Examples:

1. The equator runs through the center of Ecuador.
2. The sun is directly overhead at the equator twice a year.
3. The planet's equator is tilted at an angle of 23.5 degrees relative to its orbit.
4. The equator divides the Earth into northern and southern hemispheres.
5. The latitude of the equator is 0 degrees.