What does the term "differential pressure" refer to in pressurization control?

The term "differential pressure" in pressurization control specifically refers to the difference between the outside atmospheric pressure and the cabin pressure. This concept is crucial for maintaining a safe and comfortable environment for passengers and crew during flight, especially at higher altitudes where outside air pressure is significantly lower than at sea level. Managing this pressure difference ensures the structural integrity of the aircraft and prevents issues such as hypoxia for occupants.

While other options touch on variations in pressure, humidity, or temperature, they do not accurately capture the essence of differential pressure as it relates to cabin pressurization. The focus is solely on the relationship between the cabin interior and the atmospheric conditions outside, making the first option the correct choice in this context.