Why is Pluto not considered a planet because it’s too small, but some planets are made entirely of gas and considered planets?

Question

Edit: I know I sound like an idiot in the replies, but I’m really asking genuine questions so thank you all for being patient and answering

In: Physics

Answer 1

Because Pluto is co orbiting a second body where all the gas giants are way more massive and are the dominant gravitational body of the masses in their orbit radius.