wood

Wood is the general term for the fibrous material that forms the trunks, branches, and roots of trees and serves as a major structural and energy resource. It is a natural composite of cellulose fibers embedded in a lignin matrix, with vessels and tracheids that transport water in some species. Wood is anisotropic; its properties vary with direction, being strongest along the grain and weaker across it. Moisture content strongly affects strength, stiffness, and dimensional stability; timber used in construction is seasonally dried to reduce shrinkage and warping, commonly to around 12% moisture content in temperate climates.

Anatomy and terminology: Growth rings indicate age, and heartwood is typically denser and more decay resistant than sapwood. Branch knots and grain orientation influence mechanical behavior and appearance.

Species are commonly grouped as hardwoods, from broadleaf trees such as oak and maple, and softwoods, from conifers such as pine and spruce. Densities and strength vary widely among species, and durability for outdoor use depends on both extractives and any treatment.

Wood is processed into lumber and veneers for construction and furniture, and into engineered products such as plywood, LVL, and medium-density fibreboard to improve uniformity and stability. It is used for flooring, cabinetry, packaging, and as a fuel source in many regions. Finishing and protective coatings extend service life and resist moisture.

Sustainability-wise, wood is renewable when forests are managed responsibly. It stores carbon during growth and, when harvested and replaced, can contribute to low-embodied-energy building and materials.