The Sahara is what first comes to mind for many people when they think of "desert." But "Sahara desert" is a redundancy because the Arabic word "sahara" actually means "desert." Sahara is a subtropical desert in North Africa that is about 3.5 million square miles in size. It is comparable to the size of the United States which is about 3.7 million square miles.
Contrary to popular belief, the Sahara is not the biggest desert in the world. It is the third largest desert after the Antarctic and Arctic Polar deserts. As a non-polar desert, it is the largest.
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