Ecologically, a woodland is an area covered in trees, differentiated from a forest. In these terms, a forest has a largely closed canopy – the branches and foliage of trees interlock overhead to provide extensive and nearly continuous shade. A woodland, on the other hand, allows sunlight to penetrate between the trees, limiting shade. Woodlands may support an understory of shrubs and herbaceous plants (often including grasses). Woodlands may form a transition to shrublands under drier conditions.
Woodland is used in British woodland management to mean any smaller area covered in trees, however dense. (Forest is usually used in the British Isles only for more extensive wooded areas, again however dense – and also including Royal forests, which may not be wooded at all). The term Ancient Woodland is used in British nature conservation to refer to any wooded land established for a very long period (equivalent to the American term old growth forest).
Woodlot is a closely-related American term, which refers to a stand of trees generally used for firewood. While woodlots often technically have closed canopies, they are so small that light penetration from the edge makes them ecologically closer to woodland than forest.