What does 'isochoric' refer to in thermodynamics?

In thermodynamics, the term 'isochoric' specifically pertains to a process that occurs at constant volume. During an isochoric process, the system does not allow any change in volume, meaning that any heat added to or removed from the system will lead to a change in temperature and, potentially, pressure.

This concept is particularly important in understanding how gases behave under different thermal conditions. For example, if you heat a gas contained in a rigid, sealed container (an isochoric process), the pressure of the gas will increase as its temperature rises, since the volume remains unchanged.

The other options describe different thermodynamic processes. A process with constant pressure is termed 'isobaric', while a process with constant temperature is referred to as 'isothermal'. When pressure can change, it does not fit the description of an isochoric process, which is strictly defined by the maintenance of constant volume.