IAU Classification System:
1. A planetis a celestial body that
a. is in orbit around the Sun,
b. has sufficient mass for its self-gravity to overcome rigid body forces so that it
assumes a hydrostatic equilibrium (nearly round) shape, and
c. has cleared the neighborhood around its orbit.
2. A "dwarf planet" is a celestial body that
a. is in orbit around the Sun,
b. has sufficient mass for its self-gravity to overcome rigid body forces so that it
assumes a hydrostatic equilibrium (nearly round) shape,
c. has not cleared the neighborhood around its orbit, and
d. is not a satellite