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Which planets are classified as terrestrial planets?

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Illustration showing the eight planets of the solar system in order from the Sun-Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune-depicted to scale by size, with labeled diameters in miles and kilometers. The Sun is partially visible on the left for comparison. — Solar system The planets (in comparative size) in order of distance from the Sun.

In the solar system, the terrestrial planets are the four inner planets: Mercury, Venus, Earth, and Mars.123

These planets are distinguished from the four outer, giant planets—Jupiter, Saturn, Uranus, and Neptune—by their rocky compositions and significantly higher densities. While the giant planets are composed primarily of gases or ice, the terrestrial planets consist mainly of rock and have average densities ranging from 3.9 to 5.5 grams per cubic centimeter.243