According to Encyclopædia Britannica, Earth is classified as a terrestrial planet. A terrestrial planet is rocky, in contrast to the predominantly gas planets found in the outer solar system.
There are four terrestrial planets, all in the inner part of the solar system. Earth is the largest of these planets, with an equatorial radius measuring 3,963 miles. It has the fifth largest size and mass out of all the planets in the solar system. The name of the planet is the only planetary name to have a source of origin outside Greco-Roman mythology. The name "Earth" is derived from Germanic and Old English words.