What is definition of radiative zone?

The radiative zone is the region of the Sun extending from the core outwards where thermal radiation makes up the primary transportation of energy. In this region, a dense and hot mixture of plasma, hydrogen and helium gas undergoes continuous thermonuclear reactions, producing energy in the form of light and heat. The temperature in the radiative zone steadily increases with depth, ranging from 2 million to 7 million Kelvin, and the plasma density gradually decreases. The radiative zone extends from the core, where nuclear fusion occurs, to the convection zone, where energy is transported by convection. The radiative zone accounts for about 45% of the Sun's volume and 76% of its radius.