The term "earth radius" refers to the distance from the center of the Earth to its surface, and is used to calculate distances and elevations on the planet. There are a number of synonyms for this measurement, including "planetary radius," "terrestrial radius," and "geocentric radius." These terms all refer to the same basic measurement, but may be used in different contexts or by different groups of scientists or geographers. Other synonyms for the earth radius include "radius of the globe," "earth's equatorial radius," and "mean radius of the earth." Regardless of the term used, the earth radius remains an essential measurement for understanding our world.