Got Wood? Domestic Wood Turning Blanks Glossary of Log Terminology, Part 2

Log Terminology, Part 2 - The Tree Interior
Hardwood The term hardwood refers to the group of deciduous trees which lose their leaves on an annual basis (also called gymnosperms). The name can be misleading, however, because many hardwoods are actually not very hard at all. Balsa and basswood are examples of "hardwoods" that are quite soft in nature.
Softwood The term softwood refers to the group of non-deciduous trees which do not lose their leaves on an annual basis (also called angiosperms). This includes all conifers. The term softwood can be misleading, much like the distinction of "hardwood" because some softwoods (such as heart pine) can be quite hard...much harder, in fact, than some types of hardwoods.
Earlywood Wood which has grown during the warmer months of the year, when the growth of the tree reaches its highest rate. Latewood Wood which has grown during the colder months of the year, when the growth of the tree slows considerably. Annual Growth Rings Annual growth rings are the lines formed by the difference in color between the earlywood and latewood growth each year. Heartwood Wood contained near the center of the tree, which in some species will turn a different color from the newer, outer wood contained in the sapwood (see below). This is due, in part, to the fact that the wood no longer is used in the transportation of nutrients along the tree, and is used for the storage of wastes by the tree. Sapwood Wood contained near the outer portions of the tree responsible for the transportation of nutrients for the tree. Pith The center of a tree.
Compression Wood/Reaction Wood These terms refer to wood which grew under substantial directional force, such as a widely spread limb, or a tree growing at an angle on the side of a hill. In softwoods, this is called compression wood, and in hardwoods it is called reaction wood. Usually, in cross-section, the center of the tree typically shows up in a very off-center location, with the annual growth rings much wider, and more pronounced on one side of the center, and narrow and more compacted on the opposite side. This wood can be very difficult to work with and is prone to serious degrade while being dried, and sometimes can degrade after successful drying has taken place.