- The object must be in orbit around the Sun.
- The object must be massive enough to be a sphere by its own gravitational force. More specifically, its own gravity should pull it into a shape of hydrostatic equilibrium.
- It must have cleared the neighbourhood around its orbit
By this definition, Pluto is not a planet because it doesnt meet the 3rd requirement. Unfortunately, neither do Earth, Mars, Jupiter, and Neptune. All of those share their orbit with asteroids.
So either we do not live on a planet, or PLUTO IS AN EFFING PLANET!