Old growth forest
An old-growth forest (also termed primary forest, virgin forest, primeval forest, late seral forest, or in Britain
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

, ancient woodland
Ancient woodland
Ancient woodland is a term used in the United Kingdom to refer specifically to woodland that has existed continuously since 1600 or before in England and Wales . Before those dates, planting of new woodland was uncommon, so a wood present in 1600 was likely to have developed naturally...

) is a forest that has attained great age (and associated structural features), and thereby exhibits unique ecological features. An old growth forest has also usually reached a climax community.
Old-growth forests tend to have more large tree
A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...

s and standing dead trees, multi-layered canopies with gaps resulting from the deaths of individual trees, and coarse woody debris on the forest floor.

Forest regenerated after a severe disruption, such as wildfire, insect infestations or harvesting, is often called second-growth or regeneration until enough time passes for the effects of the disturbance to be no longer evident.