Final answer:
A rain shadow is a dry area on the leeward side of a mountain that forms due to descending dry air warming up through compression.
Step-by-step explanation:
The dry area on the leeward side of a mountain that forms as air descends and is warmed by compression is called a rain shadow. When moist air from the ocean rises up over a mountain range, it cools and its water vapor condenses, resulting in precipitation on the windward side of the mountain. As the dry air descends on the leeward side, it warms up through compression, leading to a reduction in precipitation and the formation of a rain shadow.