Definition of terrestrial

The word "terrestrial" originates from the Latin term "terrestrialis" which means "relating to the earth" or "pertaining to the earth". It was first used by astronomers in the 17th century to differentiate objects that are located on the Earth's surface or within its atmosphere from those that are found in a cosmic setting. The term "terrestrial planet" specifically refers to planets, such as Earth, Mercury, Venus, and Mars, that are situated in the habitable zone or "goldilocks zone" of their star's orbit, where the temperature is suitable for liquid water to exist on the planet's surface. These planets are generally smaller and less gaseous than other celestial bodies in the solar system, such as gas giants like Jupiter and Saturn, and ice giants like Uranus and Neptune. In summary, the term "terrestrial" is derived from the Latin word for "earth" and is used to describe objects or planets that are associated with the Earth and its environment.