Which element is most commonly associated with nuclear fusion reactions in stars?

Hydrogen is the element most commonly associated with nuclear fusion reactions in stars because it serves as the primary fuel for the processes that power stars, including our sun. In the cores of stars, hydrogen nuclei (protons) collide with enough energy to overcome their electrostatic repulsion and fuse together. This fusion process primarily occurs through the proton-proton chain reaction or the CNO cycle, and it results in the formation of helium nuclei while releasing a tremendous amount of energy in the form of light and heat. This energy production is what creates the radiation that makes stars shine.

Other elements, such as helium and carbon, play roles in later stages of stellar evolution or in specific types of stars, but hydrogen is the fundamental building block that initiates the process of fusion. Uranium, while important in nuclear fission reactions, is not typically involved in stellar nucleosynthesis in the same way hydrogen is.