Arid means extremely dry, with very little rainfall or moisture. Deserts are arid places where rain might fall only a few times per year, if at all. The Sahara Desert, the Mojave Desert, and parts of Australia are all arid regions where plants and animals have adapted to survive with almost no water.

When scientists describe a climate as arid, they mean it receives less than ten inches of rain annually. Compare that to most American cities, which get 30 to 50 inches per year. In arid environments, the air feels dry, the ground cracks, and only specially adapted plants like cacti can thrive.

The word also describes things that feel dry and lifeless in other ways. A book with endless facts but no interesting stories might be called arid. A conversation that's boring and lifeless could be described as arid, too. When you hear someone call a lecture arid, they mean it's as dull and waterless as a desert, lacking the life and interest that would make it engaging.