Succession is the change in either species composition, structure, or architecture of vegetation through time.
Vegetation has three important aspects that are subject to change.
Species composition includes the roster of the species. There can be many or few species in vegetation. Structure refers to the absolute and relative abundances and other relationships of the species constituting the community. The total number of individuals of each species, or the rank order of abundance of the different species are examples of vegetation structure. Architecture refers to the arrangement in three dimensional space of any of the elements of a community.