|wood (wd) Pronunciation Key
The thick xylem of trees and shrubs, resulting from secondary growth by the vascular cambium, which produces new layers of living xylem. The accumulated living xylem is the sapwood. The older, dead xylem in the interior of the tree forms the heartwood. Often each cycle of growth of new wood is evident as a growth ring. The main components of wood are cellulose and lignin.