A forest is an area with a high density of trees. There are many definitions of a forest, based on the various criteria. These plant communities presently cover approximately 9.4% of the Earth's surface (or 30% of total land area) and function as habitats for organisms, hydrologic flow modulators, and soil conservers, constituting one of the most important aspects of the Earth's biosphere. Historically, "forest" meant an uncultivated area legally set aside for hunting by feudal nobility, and these hunting forests were not necessarily wooded much if at all (see Royal Forest). However, as hunting forests did often include considerable areas of woodland, the word forest eventually came to mean wooded land more generally. A woodland is ecologically distinct from a forest.

The latitudes 10° north and south of the Equator are mostly covered in tropical rainforest and the latitudes between 53°N and 67°N with boreal forest.

Distribution

Forests are differentiated from woodlands by the extent of canopy coverage: in a forest the branches and the foliage of separate trees often meet or interlock, although there can be gaps of varying sizes within an area referred to as forest. A woodland has a more continuously open canopy, with trees spaced further apart, which allows more sunlight to penetrate to the ground between them (see also savanna).

Among the major forested biomes are:

• rain forest (tropical and temperate)
• taiga
• temperate hardwood forest
• tropical dry forest

Classification

thumb|right|Biogradska forest in Montenegro

• Boreal forests occupy the subarctic zone and are generally evergreen and coniferous.
• Temperate zones support both broadleaf deciduous forests (e.g., temperate deciduous forest) and evergreen coniferous forests (e.g., Temperate coniferous forests and Temperate rainforests). Warm temperate zones support broadleaf evergreen forests, including laurel forests.
• Tropical and subtropical forests include tropical and subtropical moist forests, tropical and subtropical dry forests, and tropical and subtropical coniferous forests.
• Physiognomy classifies forests based on their overall physical structure or developmental stage (e.g. old growth vs. second growth).
• Forests can also be classified more specifically based on the climate and the dominant tree species present, resulting in numerous different forest types (e.g., ponderosa pine/Douglas-fir forest).