Which process occurs without transfer of heat to the system or its surroundings?

The process that occurs without any transfer of heat to the system or its surroundings is known as an adiabatic process. In an adiabatic process, all the energy transfer that occurs is due to work being done on or by the system, with no heat entering or leaving the system. This concept is particularly important in thermodynamics, where it helps to describe processes involving gases, specifically during compression or expansion in a closed system where the walls are perfectly insulated.

Adiabatic processes can be well understood in the context of various physical phenomena, such as the rapid expansion of air in a piston or the cooling effect experienced when air rapidly expands. The absence of heat exchange leads to specific changes in temperature that can be calculated using the adiabatic relations.

In contrast, an isothermal process involves heat transfer that maintains a constant temperature, while a thermodynamic process is a broader term that encompasses any change in the state of a system and may involve heat transfer. Radiative processes specifically refer to energy transfer through electromagnetic waves, so they also involve heat exchange. Therefore, the distinctive characteristic of an adiabatic process is the lack of heat transfer, making it the correct choice for the question posed.