A secondary forest (or second-growth forest) is a forest or woodland area which has re-grown after a major disturbance such as fire, insect infestation, timber harvest or windthrow, until a long enough period has passed so that the effects of the disturbance are no longer evident. It is distinguished from an old-growth forest (primary or primeval forest), which has not undergone such disruptions, as well as third-growth forests that result from severe disruptions in second growth forests.