equatorial

Equatorial is an adjective relating to the equator, the imaginary great circle around a rotating body that is equidistant from its poles. On Earth, the equator lies at 0° latitude and divides the planet into northern and southern hemispheres. Its circumference is about 40,075 kilometers. The term also denotes things that occur, exist, or are situated near this belt.

Equatorial regions are characterized by relatively constant high temperatures and substantial annual rainfall, often supporting tropical rainforest ecosystems; they experience less seasonal variation in day length compared with higher latitudes.

In astronomy, equatorial coordinates are a celestial coordinate system built around the celestial equator. Positions of stars and other objects are specified by right ascension and declination, analogous to longitude and latitude on Earth. The system is tied to the orientation of the Earth and is a common framework for star charts and telescope pointing. Telescopes frequently use equatorial mounts that rotate around two axes, enabling smooth tracking of objects as the Earth turns. The concept also appears in other contexts, such as regions, routes, or products named "equatorial," conveying proximity to the equator or alignment with the equatorial plane. The term helps distinguish latitudinal position, climate, and observational geometry in both geographic and astronomical disciplines.