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Write as one word for noun and adjective.
Rainforest refers to both tropical and temperate continually moist forests receiving heavy rain each year. Sources vary as to the amount: not less than 80 inches but usually nearer 100 or more.
The dim light penetrating the rainforest's canopy limits low-growing, ground-rooted vegetation. Strictly speaking, rainforest is not synonymous with jungle. However, dense growth does occur along broad rivers and in previously cleared areas where strong sunlight reaches the ground; these areas may be called jungle.