Final answer:
The physiologic term that refers to the difference between inspired gas's water content and the water content of a gas at body temperature is Humidity gradient.
Step-by-step explanation:
The physiologic term that refers to the difference between inspired gas's water content and the water content of a gas at body temperature is Humidity gradient. The humidity gradient is the difference in water vapor content between two points. In this case, it is the difference in water content between inspired gas and gas at body temperature.