Final answer:
The defining characteristic of deserts is low rainfall.
Step-by-step explanation:
The defining characteristic of deserts is low rainfall. Deserts are typically arid regions with very little precipitation. This lack of rainfall is what sets deserts apart from other ecosystems. While high temperatures are often associated with deserts, they are not the defining characteristic. Not all deserts have high temperatures, as some can experience extreme cold at certain times of the year.
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