The Moon is a natural satellite
The Moon is not classified as a planet. It is Earth’s only natural satellite, which means it is a naturally formed world orbiting a planet. Earth and the Moon then travel around the Sun together.
This answer is not based on the Moon being too small or lacking geological complexity. The Moon is a rounded, differentiated world with a crust, mantle, and core. It is also larger than the dwarf planet Pluto. Size alone therefore cannot explain the label.
Why its orbit determines the category
Astronomical classifications describe relationships as well as physical properties. Under the International Astronomical Union’s Solar System definition, a planet orbits the Sun directly, has enough gravity to become nearly round, and has cleared its orbital neighborhood. The Moon instead travels around Earth, so astronomers classify it as a satellite.
The Moon still follows its own path around the Sun, but that path is inseparable from Earth’s motion. Calling it a satellite communicates which body dominates the local orbital system.
Why the Moon can seem planet-like
The Moon and Earth are unusually substantial partners compared with many planet-and-moon pairings. The Moon’s diameter is about 27 percent of Earth’s, and the system’s shared center of mass lies inside Earth but away from Earth’s exact center.
Those facts sometimes inspire the informal phrase “double planet.” It can be useful when discussing how Earth and the Moon interact, but it is not the Moon’s official classification.
A useful comparison
Ganymede and Titan are both larger than the planet Mercury, yet they are moons because they orbit Jupiter and Saturn. Pluto is smaller than Earth’s Moon, yet it is a dwarf planet because it directly orbits the Sun and fits the IAU’s dwarf-planet criteria.
The comparison shows why a body’s category cannot be inferred from a photograph or diameter. To classify a world, ask what it orbits, how it moves within that system, and which formal definition is being used.
