The term "primary planets" refers to the eight planets in our solar system that revolve around the sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. The antonyms of the term could be secondary planets, dwarf planets or celestial bodies that do not orbit around the sun, such as moons or asteroids. Secondary planets are planets that orbit around another planet, like Earth's moon or Saturn's moons. Dwarf planets, such as Pluto, cannot clear their orbits of debris and are not considered full-fledged planets. Celestial bodies like asteroids and comets are also not considered primary planets as they do not exhibit the characteristics of planets.