Why is the sun not a planet?

Answer 1

Because it's a "star", and therefore a fiery flaming mass of hydrogen gas - unlike some of the planets.

Answer 2

The sun is not considered a planet because it is a star, not a celestial body that orbits a star like a planet does. Stars generate energy through nuclear fusion in their cores, while planets do not generate energy through fusion.

Answer 3

Because it's a star.