<s>[INST] Since Pluto is no longer considered a planet, the question arises as to what exactly constitutes a planet. This question is still highly debated amongst astronomers and other scientists. One method that has been proposed to define a planet is known as the "clearing the neighborhood" criteria. According to this proposal, a planet is a celestial body that:

Is in orbit around the Sun
Has sufficient mass to assume a hydrostatic equilibrium shape 
Is dominant in its orbital zone

The first two criteria make sense, but the third criteria of being "dominant in its orbital zone" is problematic. What could this criteria mean, exactly?[/INST]