Home > Encyclopedia of Science > Tree

• Structure of a tree trunk
• Words to Know
• Tree growth
• Human use of trees

A tree is a woody perennial plant that has a single trunk arising from the ground (typically without branches near the base) and that usually grows to 20 feet (6 meters) or more in height. Branches and twigs grow from the trunk of a tree to form its characteristic leafy crown. Trees are the dominant plants in the world's forests, providing critical habitats for the other species that live there. Trees also provide many products that are important to humans, such as fruits, nuts, timber, and medicine.

Trees may be classified into two major groups: deciduous and evergreen (conifer). Deciduous trees shed their broad leaves at the end of the growing season—typically each fall. Examples of deciduous trees...