Here's a breakdown:
* Aridity: Deserts are defined by their extreme dryness. This is due to very low rainfall, often less than 10 inches (25 cm) per year.
* Other factors: While low rainfall is the defining characteristic, other factors contribute to desert formation, such as:
* High evaporation rates: Deserts have high temperatures, which cause water to evaporate quickly, further reducing moisture.
* Wind patterns: Wind can carry away any moisture that does fall, further contributing to dryness.
* Geography: Deserts can be located in rain shadows, where mountains block moisture from reaching certain areas.
It's important to note: Deserts aren't just dry places; they also have unique ecosystems with adapted plants and animals that thrive in these conditions.