Here's why:

* DNA (Deoxyribonucleic acid): The "deoxy" in its name refers to the fact that it contains deoxyribose, a sugar with one less oxygen atom than ribose.

* RNA (Ribonucleic acid): Contains ribose, which has an extra hydroxyl group (-OH) compared to deoxyribose.

This difference in sugar structure is one of the key distinctions between DNA and RNA.