Home > Encyclopedia of Science > River

• Words to Know
• Formation of rivers
• River systems
• Climactic influences
• Human control of rivers

A river is a natural stream of freshwater that is larger than a brook or creek. Rivers are normally the main channels or largest tributaries of drainage systems. Typical rivers begin with a flow from headwater areas made up of small tributaries, such as springs. They then travel in meandering paths at various speeds. Finally, they discharge or flow out into desert basins, into major lakes, or most likely, into oceans.

Sixteen of Earth's largest rivers account for close to one-half of the planet's river flow. The world's longest river is the Nile River in Africa, which runs 4,187 miles (6,739 kilometers) from its source in Burundi to...