When a refrigerant is described as saturated, it means:

When a refrigerant is described as saturated, it signifies that it is in equilibrium between its liquid and vapor phases at a specific temperature and pressure. This means that at that defined state, any addition of heat would convert some of the liquid into vapor without an increase in temperature (provided the pressure remains constant). Conversely, removing heat would cause some vapor to condense into liquid. This characteristic is critical in refrigeration cycles since it helps identify operational points within thermodynamic processes.

The other options reflect different states or conditions of refrigerants. For instance, a refrigerant that is partially vapor and partially liquid could be considered 'saturated' but is more accurately described as being in a specific range of the phase diagram rather than defining it strictly as 'saturated'. The notion of a refrigerant existing only as vapor classifies it as superheated and away from saturation. Lastly, refer to superheating, which describes refrigerant that has absorbed heat beyond the boiling point at a specified pressure, thus it is in a gaseous phase only, and does not correspond to the definition of 'saturated'.