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

This period, running from 1879 to 1912, brought unprecedented economic wealth to the Amazon, the world's largest tropical rainforest.

From Barron's ● Jul. 27, 2026

At the time, the region was likely covered by wet, dense rainforest and supported the ancestors of many animals still alive in Australia.

From Science Daily ● Jul. 19, 2026

Ms. Millard, a writer of narrative histories including 2011’s “Destiny of the Republic,” about the assassination of James A. Garfield, vividly evokes the Brazilian rainforest and its dangers.

From The Wall Street Journal ● Jul. 13, 2026

He planned to complete a programme in Peru, billed as an internship in the Amazon rainforest.

From BBC ● Jul. 11, 2026

But there was no road whatsoever across the two thousand miles of jagged mountains and thick rainforest between Mesoamerica and the Andes.

From "1491" by Charles C. Mann

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

From The Wall Street Journal ● Jul. 10, 2026

A newly discovered spider in the rainforests of northern Queensland has evolved an extraordinary hunting technique.

From Science Daily ● Jun. 26, 2026

Zoo officials said binturongs live in dense tropical and subtropical rainforests of South and Southeast Asia.

From Los Angeles Times ● Jun. 17, 2026

Rosemary Mulholland, Head of Nature Recovery with Ulster Wildlife, is part of the team that has embarked on an ambitious 100-year restoration programme to restore temperate rainforests.

From BBC ● May 25, 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