What is Planet?

General objective of this lecture is to present on What is Planet. The definition of planet, since the word was coined by the ancient Greeks, has included within its scope a wide range of celestial bodies. A planet is a celestial body that is in orbit around the Sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and has cleared the neighborhood around its orbit.