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

The exterior of the single-story, five-door apartment complex where she resides is almost completely paved — nothing like the rainforest terrain of her youth.

From Los Angeles Times ● Sep. 2, 2026

Atlantic puffins are the harlequins of the sea, colorful as a rainforest parrot—black backs, white bellies, quad-colored beaks and intensely orange feet and legs.

From The Wall Street Journal ● Aug. 26, 2026

Lula is credited with restoring social programs dismantled by his predecessor, curbing the destruction of the Amazon rainforest, and putting Brazil's democracy back on a more secure footing.

From Barron's ● Aug. 2, 2026

In 2024, the Amazon rainforest experienced its worst forest fires in over two decades, which the Copernicus Climate Change Service put down to "climate extremes and human activity".

From BBC ● Jul. 21, 2026

Since then countless campaigns to save the rainforest have driven home its lesson: development in tropical forests destroys both forests and their developers.

From "1491" by Charles C. Mann

Though it was always grittier than the beaches and rainforests that draw millions of tourists, residents said that until the past few years it felt like a relatively safe place to live.

From The Wall Street Journal ● Aug. 27, 2026

In the rainforests of South America and Southeast Asia, they became specialized hunting companions capable of following prey through thick vegetation and moving across difficult terrain.

From Science Daily ● Aug. 10, 2026

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

From The Wall Street Journal ● Jul. 10, 2026

Their team, from Australia's Macquarie University, spent 10 nights in the tropical rainforests of northern Queensland, capturing the spider's behaviour using high-speed and infrared cameras.

From BBC ● Jun. 23, 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