Air-dried – Dried by exposure to air in a yard or shed, without artificial heat.
Birdseye – Small localized areas in wood with the fibers indented and otherwise contorted to form few to many small circular or elliptical figures remotely resembling birds’ eyes on the tangential surface. Sometimes found in sugar maple and used for decorative purposes; rare in other hardwood species.
Bark Pocket – An opening between annual growth rings that contains bark. Bark pockets usually appear as dark streaks on radial surfaces and rounded areas on tangential surfaces.
Board Foot – A unit of measurement of lumber represented by a board 12 in. long, 12 in. wide, and 1 in. thick or its cubic equivalent. In practice, the board foot calculation for lumber 1 in. or more in thickness is based on its nominal thickness and width and the actual length. Lumber with a nominal thickness of less than 1 in. is calculated at 1 in.
Box Beam – A built-up beam with solid wood flanges and plywood or wood-based panel product webs.
Boxed Heart – The term used when a pith falls entirely within the four faces of a piece of wood anywhere in its length. Also called boxed pith.
Cant – A log that has been slabbed on one or more sides. Ordinarily, cants are intended for resawing at right angles to their widest sawn face. The term is loosely used.
Check – A lengthwise separation of the wood that usually extends across the rings of annual growth and commonly results from stresses set up in wood during seasoning.
Cup – A distortion of a board in which there is a deviation flatwise from a straight line across the width of the board.
Density – As usually applied to wood of normal cellular form, density is the mass per unit volume of wood substance enclosed within the boundary surfaces of a wood-plus-voids complex. It is variously expressed as pounds per cubis foot, kilograms per cubic meter, or grams per cubic centimeter at a specified moisture content.
Figure – The pattern produced in a woods surface by annual growth rings, rays, knots, deviations from regular grain such as interlocked and wavy grain, and irregular coloration.
Flitch – A portion of a log sawn on two or more faces – commonly on opposite faces leaving two waney edges. When intended for resawing into lumber, it is resawn parallel to its original wide faces. Or, it may be sliced or sawn into veneer, in which case the resulting sheets of veneer laid together in the sequence of cutting are called a flitch.
Grade – The designation of the quality of a manufactured piece of wood or of logs.
Grain – The direction, size, arrangement, appearance, or quality of the fibers in wood or lumber.
Green – Freshly sawed or undried wood. Wood that has become completely wet after immersion in water would not be considered green but may be said to be in the “green condition.”
Growth Ring – The layer of wood growth put on a tree during a single growing season. In the temperate zone, the annual growth ring of many species (for example, oaks and pines) are readily distinguished because of differences in the cells formed during the ealry and late parts of the season. In some temperate zone species (black gum and sweetgum) and many tropical species, annual growth rings are not easily recognized.
Hardness – A property of wood that enables it to resist indentation.
Hardwoods – Generally one of the botanical groups of trees that have vessels or pores and broad leaves, in contrast to the conifers or softwoods. The term has no reference to the actual hardness of the wood.
Heartwood – The wood extending from the pith to the sapwood, the cells which no longer participate in the life processes of the tree. Heartwood may contain phenolic compounds, gums, resins, and other materials that usually make it darker and more decay resistant than sapwood.
Honeycombing – Checks, often no visible at the surface, that occur in the interior of a piece of wood, usually along the wood rays.
Kiln – A chamber having controlled air-flow, temperature, and relative humidity for drying lumber. The temperature is increased as drying progresses, and the relative humidity is increased.
Kiln-dried – Dried in a kiln with the use of artificial heat.
Knot – That portion of a branch or limb that has been surrounded by subsequent growth of the stem. The shape of the knot as it appears on a cut surface depends on the angle of the cut relative to the long axis of the knot.
Millwork – Planed and patterned lumber for finish work in buildings, including items such as sash, doors, cornices, panelwork, and other items of interior or exterior trim. Does not include flooring, ceiling, or siding.
Mineral Streak – An olive to greenish-black or brown discoloration of undetermined cause in hardwoods.
Moulding – A wood strip having a curved or projecting surface, used for decorative purposes.
Mortise – A slot cut into a board, plank, or timber, usually edgewise, to recieve the tenon of another board, plank, or timber to form a joint.
Old Growth – Timber in, or from, a mature, naturally established forest. When the trees have grown most if not all of their individual lives in active competition with their companions for sunlight and moisture, this timber is usually straight and relatively free of knots.
Overlay – A thin layer of paper, plastic, film, metal foil, or other material bonded to one or both faces of panel products or to lumber to provide a protective or decorative face or a base for painting.
Pitch Pocket – An opening extending parallel to the annual growth rings and containing, or that has contained, pitch, either solid or liquid.
Pith – The small, soft core occuring near the center of a tree trunk, branch, twig, or log.
Plainsawn – Also, Flatsawn, Flatgrained. Lumber that has been sawn parallel to the pith and approximately tangent to the growth rings. Lumber is considered flat grained when the annual growth rings make an angle of less than 45° with the surface of the piece.
Quartersawn – Lumber that has been sawed so that the wide surfaces extend approximately at right angles to the annual growth rings. Lumber is considered quartersawn when the rings form an angle of 45° to 90° with the wide surface of the piece.
Rip – To cut lengthwise, parallel to the grain.
Rough Lumber – Lumber that has not been dressed (surfaced) but has been sawed, edged, and trimmed.
Sapwood – The wood of pale color near the outside of the log. Under most conditions, the sapwood is more susceptible to decay than heartwood.
Scarf Joint – An end joint formed by joining with adhesive the ends of two pieces that have been tapered or beveled to form sloping plane surfaces, usually to a featheredge, and with the same slope of the plane with respect to the length in both pieces. In some cases, a step or hook may be machined into the scarf to facilitate alignment of the two ends, in which case the plane is discontinuous and the joint is known as a stepped or hooked scarf joint.
Softwoods – Generally, one of the botanical groups of trees that have no vessels and in most cases, have needle-like or scale-like leaves, the conifers, also the wood produced by such trees. The term has no reference to the actual hardness of the wood.
Stickers – Strips or boards used to separate the layers of lumber in a pile and thus improving air circulation.
Tangential – Strictly, coincident with a tangent at the circumference of a tree or log, or parallel to such a tangent. In practice, however, it often means roughly coincident with a growth ring. A tangential section is a longitudinal section through a tree or limb perpendicular to a radius. Flat-grained lumber is sawed tangentially.
Tenon – A projecting member left by cutting away the wood around it for insertion into a mortise to make a joint.
Veneer – A thin layer or sheet of wood.
Vertical Grain – See Quartersawn Grain.
Definitions from Wood Handbook printed by the Forest Products Society in 1999.