This trunk typically contains woody tissue for strength, and vascular tissue to carry materials from one part of the tree to another.
Under such a definition, herbaceous plants such as palms, bananas and papayas are not considered trees regardless of their height, growth form or stem girth.
Certain monocots may be considered trees under a slightly looser definition; Trees have modified structures such as thicker stems composed of specialised cells that add structural strength and durability, allowing them to grow taller than many other plants and to spread out their foliage.
Because of their longevity and usefulness, trees have always been revered, with sacred groves in various cultures, and they play a role in many of the world's mythologies.
Diagram of secondary growth in a eudicot or coniferous tree showing idealised vertical and horizontal sections.
Trees are not a taxonomic group but include a variety of plant species that have independently evolved a woody trunk and branches as a way to tower above other plants to compete for sunlight.
Trees tend to be long-lived, some reaching several thousand years old.
Below the ground, the roots branch and spread out widely; they serve to anchor the tree and extract moisture and nutrients from the soil.
Above ground, the branches divide into smaller branches and shoots.
If insufficient water is available the leaves will die.