The Sun (太陽 Taiyō) is the star at the center of the Solar System.
The Sun has a minor role in several of the Dragon Ball movies: in Dragon Ball: Sleeping Princess in Devil's Castle, Lucifer wants to get rid of the Sun so he can take over the Earth; Lord Slug blocks out the Sun with a cloud produced by a special machine in order for his henchmen to survive on Earth without their special equipment. Later in the movie, Goku uses the energy of the Sun to make a Spirit Bomb and crushes the machine and Slug along with it. Cooler (in Dragon Ball Z: Cooler's Revenge), Parallel Broly (in Dragon Ball Z: Broly - Second Coming), and Baby (in Dragon Ball GT) are all defeated by being blasted into the Sun by a Family Kamehameha. Ironically, in the Funimation dub of the first example, Cooler considered destroying it to have the planet and any surrounding planets freeze in the resulting darkness, although he was forced to discard this plan when realizing that he himself was headed for it.
Suns of the universe
There are several other suns in the universe. Namek has three suns, and Planet Vegeta has two suns. Coola No. 98 is also located in a solar system with two suns. There are several suns in the Sacred World of the Kai, but only one gigantic sun in the Other World. Beerus' planet has two suns but at some point in time, he destroyed both until Whis did Temporal Do-Over, gaining the suns back. In Dragon Ball GT, there is a sun behind of the Deserted Starship which is 70x Earth's normal gravity.