What is the largest desert in the world?

• A. Gobi
• B. Sahara
• C. Arabian
• D. Kalahari

Answer: (B)

Deserts are defined by aridity, meaning very low precipitation, not by how much sand or heat they have. When you compare deserts by area, the largest in the world is Antarctica, a polar desert that covers a huge area with very little annual precipitation. Among the warm, sandy deserts people usually talk about, the Sahara is the biggest, spanning roughly 9.2 million square kilometers, which makes it larger than the Gobi, the Arabian Desert, or the Kalahari. So, in this set of options, the Sahara is the best-known largest desert and is why that choice fits the question here. (If you were considering deserts in general, noting Antarctica would be important, but the common emphasis in many quizzes is on hot deserts.)