rainforest

American  

[reyn-fawr-ist, ‐-for‐] / ˈreɪnˌfɔr ɪst, ‐ˌfɒr‐ /

Or rain forest

noun

rainforests plural

1. a tropical forest, usually of tall, densely growing, broad-leaved evergreen trees in an area of high annual rainfall.

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rainforest British  

/ ˈreɪnˌfɒrɪst /

noun

1. Also called: selva.  dense forest found in tropical areas of heavy rainfall. The trees are broad-leaved and evergreen, and the vegetation tends to grow in three layers (undergrowth, intermediate trees and shrubs, and very tall trees, which form a canopy)

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rainforest Scientific  

/ rān′fôr′ĭst /

1. A dense evergreen forest with an annual rainfall of at least 406 cm (160 inches).

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Closer Look

Most of the world's rainforests lie near the equator and have tropical climates. However, cooler rainforests exist in the Pacific Northwest region of the United States and Canada. The world's largest rainforest is located in the Amazon River basin. The Amazon rainforest has been described as the “lungs of our planet” because it continuously recycles carbon dioxide into oxygen, with a significant percentage of the world's atmospheric oxygen being produced in this region. Besides helping to regulate the world's climate, rainforests host an extraordinary diversity of life. Scientists believe that as many as half of the Earth's different species of plants and animals are found only in the rainforests, which take up a mere 7 percent of the world's landmass. By some estimates, more than half of the Earth's original rainforests have already been burned or cut down for timber or grazing land, and more than 130 plant, animal, and insect species are thought to be going extinct daily as a result of the lost habitat. Currently 25 percent of Western pharmaceuticals are derived from tropical rainforest ingredients, and 70 percent of the plants with anticancer properties are found only in this shrinking biome.

Other Word Forms

Noun Inflected Forms

• rainforests
  plural

Etymology

Origin of rainforest

First recorded in 1900–05

Explanation

A rainforest is a dense, damp forest with a huge number of different kinds of plants and animals. Scientists believe there may be millions of species in rainforests that haven't been discovered yet. There are two kinds of rainforests, tropical and temperate. Temperate rainforests are much smaller, and there are fewer of them. Most rainforests in the United States (in the Pacific Northwest and Alaska) are temperate. Tropical rainforests are remarkably wet and warm, with frequent rain and thick growth of trees and plants. Hawaii has the US's only tropical rainforests.

Example Sentences

See Examples For:

rainforest rainforests

Flames engulfed the world's largest tropical rainforest in 2024 when an unprecedented drought triggered the spread of fires, the majority of which were man-made.

From Barron's ● Jul. 21, 2026

The amount of land burned in the world's largest rainforest last year covered the smallest area since MapBiomas records began in 1985.

From BBC ● Jul. 21, 2026

Many then pay several thousand dollars to smugglers known as coyotes who take them on a grueling journey across the Brazilian border deep in the Amazon rainforest.

From The Wall Street Journal ● Jul. 14, 2026

The plan would see India send several of its more than 3,600 tigers to southwest Cambodia's Cardamom Mountains, a protected expanse of lush rainforest stretching over a million hectares.

From Barron's ● Jul. 8, 2026

Then, wearing only my undershorts, and streaked head to foot with mud like one of those lost guys from the Amazon rainforest, I went in to break the news to Mom.

From "Tangerine" by Edward Bloor

Tropical rainforests like the Amazon are home to millions of species, and in a healthy state they absorb vast quantities of planet-warming carbon dioxide, helping to keep the Earth cool.

From BBC ● Jul. 21, 2026

Hailing from the rainforests of Sumatra, Indonesia, corpse flowers are a massive, putrid spectacle.

From The Wall Street Journal ● Jul. 10, 2026

The butterflies belong to the Heliconius tribe, a group found across the rainforests of Central and South America.

From Science Daily ● Jun. 22, 2026

“We traveled to 16 rainforests, we sought and received all necessary permissions,” Anadol says.

From Los Angeles Times ● Jun. 5, 2026

To the north, the hills and rainforests of Lynn Canyon Park snaked between the subdivisions of North Vancouver until they gave way to the wilderness.

From "The Son of Neptune" by Rick Riordan