In woodworking terminology, the term “hardwood” is not strictly a term referring to hardness, but rather to the botanical designation of the trees from which the wood comes. In short, hardwoods are angiosperms (flowering plants)—while softwoods are classified as cone-bearing plants (conifers). For practicality’s sake, it just so happens that most hardwoods happen to yield fairly hard wood, so the name “hardwood” is generally applied, though not always strictly correct. (For instance, Balsa is a flowering plant, and is technically considered a hardwood.)
Families of hardwoods
Fabaceae (legume family)
Rosaceae (rose family)
Characteristics of the wood of angiosperms
Anatomically, the most noticeable element of all hardwoods is the presences of pores, sometimes called vessels. These vessels usually appear as small openings in the wood when viewing the endgrain. Noting the size, arrangement, and contents of the pores is generally the first step in attempting to identify a hardwood.
Please see the following page for more in-depth information on hardwood anatomy.