* Orbits a planet: Ganymede orbits Jupiter, which is a planet. By definition, a moon orbits a planet.
* Not a primary body: Ganymede is not the primary body in its system. It is a satellite of Jupiter, meaning it is gravitationally bound to Jupiter and orbits it.
* Does not clear its neighborhood: One of the criteria for a celestial body to be classified as a planet is that it must have cleared its neighborhood of other objects. Ganymede shares its orbital space with other moons of Jupiter, and it does not dominate the region.
While Ganymede is the largest moon in our solar system, and even bigger than the planet Mercury, it still fits the definition of a moon due to its relationship with Jupiter.
