Wood is a dynamic medium. Like all organic materials, it has character and quirks, responds to its environment, and changes over time. Because of its “personality,” wood should be treated with understanding and a certain amount of care. For wood flooring professionals, knowing about the properties of wood in general, as well as those of individual wood species, is critical to proper installation. For consumers, it’s important to have realistic expectations about how wood will perform. Most wood used for flooring is essentially a byproduct of more expensive wood-consuming industries (furniture manufacture, for example), so it is usually not the highest grade of lumber. However, it is quite economical in comparison. This publication provides an overview of the mechanical and physical properties of wood, followed by more detailed information on several species used in flooring. In selecting the species described, the aim has been to offer a fair sampling of some of today’s most popular woods.