A stream is any body of flowing fluid. The most familiar type of stream is made of water, although streams can also be made of air, lava, electricity, or any other fluid.

Jet streams, for instance, are cold, fast-moving winds that circulate high in the atmosphere. Lightning is a stream of electricity that circulates from cloud to cloud, from the cloud to the ground, or even from the ground to a cloud. Hydrothermal vents eject a stream of vent fluid into the ocean that surrounds them. Although vent fluid contains water, it is much, much hotter than the water surrounding it, and filled with materials from the Earth's crust, such as sulfur, zinc, and copper. Vent fluid is sometimes visible as white or black streams pouring from the vent.

Still, the most familiar type of stream is made of free-flowing water. These streams are fed by rain, melting snow and ice, and groundwater—the water that penetrates deeper into the Earth after the surface soil is completely soaked. Streams vary in size from tiny rills or streamlets, to larger brooks, creeks, and rivers. The term “stream” is often used interchangeably with “river,” though “stream” usually refers to a smaller body of water.

Streams take on different shapes depending on the landscape through which they flow. Cascades, or waterfalls, are formed when shallow water flows over and around large rocks. Normally, waterfalls are found in mountainous areas.

A stream containing large amounts of sediment lining its bottom and sides can change its shape and develop large curves called meanders. Sometimes, meanders are so wide that they eventually are cut off from the main stream. The U-shaped body of water left behind is called an oxbow lake.

Large amounts of sediment in a stream may cause it to split into many intertwined channels, called braided channels. Braided rivers are different from meandering streams. While meandering streams find a single new channel, braided streams flow over a series of wide, shallow channels.

Human engineering efforts can change the flow of a stream. For example, a meander might be straightened to improve a shipping channel.

Multiple streams can flow together so that one stream eventually carries water that originated from different parts of a large area. This area is known as the stream’s drainage basin, or watershed. The Amazon River in South America is the world’s largest stream and also has the world’s largest drainage basin. At more than 6.9 million square kilometers (2.3 million square miles), it is nearly as large as the entire country of Australia.

stream
Little streams turn into big rivers.

Nile v. Amazon
The Nile and Amazon rivers have shared a long rivalry to determine which is the world's longest stream. Stretching 6,695 kilometers (4,160 miles) from its source in Burundi to its mouth in the Mediterranean Sea, the Nile is generally considered the longest. However, in 2007, a team of Brazilian scientists claimed to have found a new starting point for the Amazon River, 6,800 kilometers (4,225 miles) from its mouth.

Noun

layer of gases surrounding Earth.

Amazon River
Noun

(6,280 kilometers/3,900 miles) longest river in South America.

Noun

layers of gases surrounding a planet or other celestial body.

braided river
Noun

flowing body of water separated into channels by tiny islands.

brook
Noun

small flow of water, larger than a rill but smaller than a river.

cascade
Noun

shallow waterfall over rocks.

channel
Noun

deepest part of a shallow body of water, often a passageway for ships.

circulate
Verb

to move around, often in a pattern.

Noun

visible mass of tiny water droplets or ice crystals in Earth's atmosphere.

copper
Noun

chemical element with the symbol Cu.

creek
Noun

flowing body of water that is smaller than a river.

Noun

rocky outermost layer of Earth or other planet.

drainage basin
Noun

an entire river system or an area drained by a river and its tributaries. Also called a watershed.

earth
Noun

soil or dirt.

eject
Verb

to get rid of or throw out.

electricity
Noun

set of physical phenomena associated with the presence and flow of electric charge.

engineering
Noun

the art and science of building, maintaining, moving, and demolishing structures.

fluid
Noun

material that is able to flow and change shape.

Noun

water found in an aquifer.

hydrothermal
Adjective

related to hot water, especially water heated by the Earth's internal temperature.

Noun

water in its solid form.

Noun

winds speeding through the upper atmosphere.

Noun

the geographic features of a region.

lava
Noun

molten rock, or magma, that erupts from volcanoes or fissures in the Earth's surface.

Noun

sudden electrical discharge from clouds.

meander
Noun

large curve in a lake or stream.

Noun

large body of salt water that covers most of the Earth.

Noun

lake formed from an abandoned bend in a river.

penetrate
Verb

to push through.

Noun

liquid precipitation.

rill
Noun

very small stream.

Noun

large stream of flowing fresh water.

Noun

solid material transported and deposited by water, ice, and wind.

shipping channel
Noun

deep waterway where large boats regularly transport goods and people.

snow
Noun

precipitation made of ice crystals.

soil
Noun

top layer of the Earth's surface where plants can grow.

stream
Noun

body of flowing fluid.

sulfur
Noun

chemical element with the symbol S.

vent
Noun

crack in the Earth's crust that spews hot gases and mineral-rich water.

visible
Adjective

able to be seen.

Noun

flow of water descending steeply over a cliff. Also called a cascade.

Noun

entire river system or an area drained by a river and its tributaries.

Noun

movement of air (from a high pressure zone to a low pressure zone) caused by the uneven heating of the Earth by the sun.

zinc
Noun

chemical element with the symbol Zn.