木材和木材产品(wood)
木材为树干和树根中坚硬的纤维状物质。木材的截面分为髓心、木质部和树皮。在树皮和木质部之间，尚有一层树木生长的细胞。木质部在髓心周围一圈圈地向外生长，每年一圈，称作生长轮。在横截面上可看到心材与边材的区别。心材颜色较深；而边材则是心材周围颜色较浅的部分，它含有的细胞具有吸取水分和矿物质及涵养枝叶的作用。木材是地球上最丰富和最广的天然材料，与煤炭、矿物及石油等不同，它可以再生。使用得最多的木材来自两类树木：针叶树或软材（如松、云杉及冷杉）；阔叶树或硬材（如栎树、胡桃树及枫树）。木材因含水率的变化而产生膨胀和收缩。木材的力学性质包括强度、硬度和相对密度。木材具有隔热、绝缘和良好的声学性质。木材的种类可以从它的颜色、气味、纹理和重量等加以识别。商业上所制成的产品木料和胶合板至纸张，自漂亮的家具至牙签，估计有一万种之多。木材及其加工後的下脚料也是许多化工制品，包括赛璐玢、木炭、染料、炸药、漆和松节油的基本原料。木材还可用作燃料。
English version：
wood
Hard, fibrous material formed by the accumulation of secondary xylem produced by the vascular cambium. It is the principal strengthening tissue found in the stems and roots of trees and shrubs. Wood forms around a central core (pith) in a series of concentric layers called growth rings. A cross section of wood shows the distinction between heartwood and sapwood. Heartwood, the central portion, is darker and composed of xylem cells that are no longer active in the life processes of the tree. Sapwood, the lighter area surrounding the heartwood, contains actively conducting xylem cells. Wood is one of the most abundant and versatile natural materials on earth, and unlike coal, ores, and petroleum, is renewable with proper care. The most widely used woods come from two groups of trees: the conifers, or softwoods (e.g., pine, spruce, fir), and the broadleaves, or hardwoods (e.g., oak, walnut, maple). Trees classified as hardwoods are not necessarily harder than softwoods (e.g., balsa, a hardwood, is one of the softest woods). Density and moisture content affect the strength of wood; in addition to load-bearing strength, other variable factors often tested include elasticity and toughness. Wood is insulating to heat and electricity and has desirable acoustical properties. Some identifying physical characteristics of wood include color, odor, texture, and grain (the direction of the wood fibers). Some 10,000 different wood products are commercially available, ranging from lumber and plywood to paper, from fine furniture to toothpicks. Chemically derived products from wood and wood residues include cellophane, charcoal, dyestuffs, explosives, lacquers, and turpentine. Wood is also used for fuel in many parts of the world.
