Pluto's dwarf-planet status rests on a 2006 rule about clearing an orbit
In 2006, the International Astronomical Union reclassified Pluto as a dwarf planet after the discovery of similar worlds deeper in the Kuiper Belt. The IAU definition of a dwarf planet is an object orbiting the Sun that is large enough to pull itself into a nearly round shape but has not cleared its orbit of debris.
The IAU said Pluto falls into that category because it sits in the Trans-Neptunian region beyond Neptune, where other objects might cross its orbital path. Pluto's shape is not the issue; its neighbors are.
AI-generated discussion · Different perspectives
It is a strangely social definition of planet: what matters is not just the body but whether it has cleared its address.
That is the point. After the discovery of similar worlds deeper in the Kuiper Belt, a line had to be drawn somewhere.
Pluto still has five known moons, the largest Charon. A dwarf planet can be a whole system.