Terms and Abbreviations

Air Dried Removing moisture from green wood by exposing to the air usually in a yard without artificial heat. Not a complete drying process for interior woodwork.
Angiosperm Belonging to the class of plants having seeds enclosed in an overlay. Within this class, the subclass dicotyledons includes all hardwood trees.
Back The side reverse to the face of a panel or the poorer side of a panel in any grade of plywood calling for a face and back.
Backing Board The board remaining on faceplate after slicing veneer. Usually thin boards (½" to ¾" thick). Generally backing boards are quarter sawn and make beautiful stable wood floors, paneling etc.
Balanced Matched Two or more veneer components or leaves of equal size to make up a single face.
Balanced Panel Plywood thickness composed of an odd number of veneers. A balanced panel is one which is free of warp that affects serviceability for its intended use.
Band Sawn Saw blade tooth markings (kerf) on face at right angle to edge of board.
Bark Pocket Bark around which normal wood has grown.
Bird Peck A patch of distorted grain resulting from birds pecking; sometimes containing ingrown bark.
Bird's Eye Small decorative circular figure, common in Hard Maple.
Blending Color change that is detectable at a distance of 6 feet to 8 feet but which does not detract from the overall appearance of the panel.
Board Foot A piece of lumber 1 inch thick,12 inches wide and 1 foot long, or its cubic equivalent.
Book Matched Adjacent veneer sheets are opened like a book, matching the back of one sheet with the face of the next. Opposite slant of grain creates a light and dark effect (tight and loose veneers).
Bow The distortion in a board that deviates from flatness within the length of the board (board shaped like the bow of a bow & arrow).
Brashness Condition of wood characterized by low resistance to shock and by abrupt failure across the grain without splintering.
Burl A burl is a swirl or twist in the grain of the wood which does not contain a knot (figured wood around a knot).
Burl, Blending A swirl, twist, or distortions in the grain of the wood which usually occurs near a knot or crotch but does not contain a knot and does not contain abrupt color variation. A blending burl is detectable at 6 feet to 8 feet as a swirl or roundel.
Burl, Conspicuous A swirl, twist, or distortion in the grain of the wood which usually occurs near a knot of crotch. A conspicuous burl is associated with abrupt color variation and/or a cluster of small dark piths caused by a cluster of adventitious buds.
Cambium (Vascular Cambium) The actively dividing layer of cells that lies between the bark and the sapwood and gives rise to secondary xylem and phloem or, in other words, the layer of tissue just beneath the bark from which the new wood and bark cells of each year's growth develop (the growing part of a tree).
Cathedral A grain appearance characterized by a series and inverted "V" or cathedral type patterns common in plain-sliced (flat-cut) veneer.
Cell A chamber or component at some time containing a protoplast; a general term fro the minute units of wood structure. It includes fibers, vessel segments and other elements of diverse structure and functions.
Cell Wall The limiting membrane of a cell
Cellulose The carbohydrate that is the principal constituent of wood and forms the framework of the cells.
Centers Inner plies whose grain direction runs parallel to that of the outer plies in veneer core plywood.
Center Match An even number of veneer components or leaves of equal size matched with a joint in the center of the panel to achieve horizontal symmetry or balance.
Check a lengthwise separation in the wood surface caused by rapid or faulty seasoning.
Circular Sawn Saw blade tooth marking are curved on the face of a board. Lumber sawn by a Circular Saw.
Clear Face Cutting A cutting having one clear face.
Close Grain Wood with narrow growth rings.
Course Grain "Rapid growth" wood with wide growth rings.
Collapse The flattening of single cells or row of cells in hardwood during the drying or pressure treatment of wood, characterized externally by a caved-in or corrugated appearance. Also, termed Honeycomb.
Color Change Most woods darken after finishing (Walnut is an exception).
Comb Grain a quality of rift cut veneer with exceptionally straight grain and closely spaced growth increments resembling the appearance of long strands of combed hair.
Component (Of Face) A individual piece of veneer that is jointed to other pieces to achieve a full length and width face. Terms used interchangeably with components in the context of the face and piece and leaf of veneer.
Conditioning in Kiln Drying Obtaining the same moisture content in the "shell" or outside surface of the board as there is in the "core" or center of the board.
Core The inner part of plywood between face and back, usually veneer. Sawn lumber, particleboard, MDF, and hardboard are also used as core.
Crossbanding Veneer used in the construction of plywood with five or more plies. Crossbands are placed at right angles to the grain of the faces and typically placed adjacent to the face and back. Also refers to all inner layers of veneer whose grain direction runs perpendicular to that of the outer plies and includes parallel laminated plies.
Cross Bar Irregularity of grain resembling a dip in the grain running at right angles, or nearly so, to the length of the veneer.
Cross Break Separation of the wood cells, often appearing as barely distinct fine irregular lines across the grain. Such breaks are often due to internal stains resulting form unequal longitudinal shrinkage or to external forces. (Shake).
Cross Figure A series of naturally occurring figure effects characterized by mild or dominate pattern across the grain in some faces. For example, a washboard effect occurs in fiddle-back cross figure; and cross wrinkles occur in the mottle figure (decorative design of grain).
Cup The distortion in a board that deviates flatwise from a straight line across the width of the board.
Cutting A portion of a board or plank obtained by cross-cutting or ripping or by both. Diagonal cutting is not permitted.
Decay Disintegration of wood substance due to the action of wood-destroying fungi...wood turns white in color.
Deciduous The term given to broad-leaved trees which shed leaves annually. Examples: Ash, Oak and Walnut (Hardwood trees).
Defects The most common defects includes knots, worm holes, bird pecks (bark pockets), wane, stain, pith, checks, unsound burls, shake and split.
Delamination The separation of veneers in plywood thorough failure of the adhesive.
Density Wood weight per, unit volume. Durability, hardness, and toughness usually increase with density (the weight of one cubic foot of a lumber product.)
Dimension Lumber Lumber cut, or S4S, to predetermined specific width (sometimes also to length). 1" x 4," 2" x 4," 2" x 6," 4" x 4" - 8, etc. (Note: both hardwood and softwood dimension lumber are piece tallied and not measured with a board rule.)
Discolorations Stains in wood substances, Common veneer stains are sap stains, blue stains, stain produced by chemical action caused by the iron in the cutting knife coming in contact with the tannic acid of the wood, and those resulting from exposure of natural wood extractives to oxygen and light, to chemical action of vat treatments or the adhesive components, and/or to the surface finish.
Doze (synonymous with DOTE) A form of incipient decay characterized by a dull and lifeless appearance of the wood, accompanied by a loss of strength and softening of the wood substance.
End Check Separation of the wood fibers at the end of a board.
End Grain Lumber grain as seen from one end of a board.
End Matched Tongue and grooved on ends of boards as well as the sides (as in Oak flooring).
Even Texture Uniform texture showing little contrast between spring growth and summer growth.
Equalizing in Kiln Drying Obtaining the same moisture content from board to board in a kiln charge of lumber. This process is after lumber is kiln dried.
Face The better side of any plywood panel in which the outer plies are of different veneer grades. Also, either side of a panel in which there is no difference in the veneer grade of the outer plies.
FAS First and Seconds is the top grade recognized by the NHLA. This is the Face grade of FAS 1 Face and must yield a minimum of 83.3% clear face cutting. NOTE: This is not a "Clear" grade.
F.E.Q. First European Quality is the top grade purchased in Europe. This grade mainly applies to the species the United States imports from other countries The F.E.Q. grade is superior to our FAS grade as far as lumber quality.
FEW (Concerning Plywood Face Grades) A small number of characteristics without regard to their arrangement in the panel.
Fiberboard Panel board made from wood fiber wood fiber or pulp bonded with adhesive; plywood substitute.
Fiddleback A grain characteristic that has a rippled appearance (Maple, Mahogany and Sycamore). veneers used on violins.
Figure The pattern produced in a wood surface by annual growth rings, rays, knots, deviations from natural grain such as interlocked, curly and wavy grain and irregular coloration.
Flake See fleck ray.
Flat-Cut See plain-sliced.
Fleck, Ray Portion of a ray as it appears on the quartered surface. Fleck is often a dominate appearance feature in quartered Oak.
Flitch A complete bundle of veneer sheets laid together in sequence as they are cut from a given log or section of a log.
Gap Open slits in the inner plies or improperly joined veneers.
Grain The direction, size, arrangement and appearance of the fibers in wood or veneer. The 8' grain direction in 4' x 8' plywood.
Grain Slope Expression of the angle of the grain to the long edges of the veneer component.
Grain Sweep Expression of the angle of the grain to the long edges of the veneer component over the area extending one-eight of the length of the piece from the ends.
Green Lumber Freshly sawn; unseasoned lumber.
Gross Lumber Tally Lumber measured when freshly cut. NOTE: Lumber will shrink from 3% to 11% after kiln drying....depending on the species.
Growth Rings New wood formed by the annual growth of a tree (Also called annual rings).
Gum Pockets Well-defined openings between rings of annual growth, containing gum or evidence of prior gum accumulations.
Gum Spots and Streaks Gum or resinous material or color spots and streaks caused by prior resin accumulations sometimes found on panel and lumber surfaces. especially common in Cherry.
Gymnosperm The class of plants having naked seeds (not enclosed in an ovary). Within this group are all trees yielding softwood lumber.
Hairline A thin, perceptible line showing at the joint of two pieces of wood.
Half-Round A method of veneer cutting similar to rotary cutting except that the piece being cut is secured to a "stay log," a device that permits the cutting of log on a wider sweep than when mounted with its center secured in the lathe to produce rotary sliced veneer. A type of half round cutting is used to achieve plain-sliced or flat-cut veneer.
Hardboard Homogeneous panels manufactured primarily from inter-felted lignocellulosic (wood) fibers consolidated under heat and pressured with a density of (31 lb./cu.ft.) or more often termed "masonite."
Hardwood General term used to designate lumber or veneer produced from temperate zone deciduous or tropical broad-leaved trees in contrast to softwood, which is produced form trees which usually needled bearing or coniferous. The term does not infer hardness in its physical sense.
Heartwood The non-active or dormant center of a tree generally distinguishable from the outer portion (sapwood) by its darker color. Heartwood is more decay-resistant than sapwood.
Honeycomb A cellular separation that occurs in the interior of a board, usually along the wood rays.
Hygroscopic Wood products absorb moisture and expand when exposed to high humidity and expel moisture and shrink in low humidity environments, changing and balancing with its general surroundings.
Inconspicuous Barely detectable with the naked eye at a distance of 6 feet to 8 feet (See Blending).
Inner Plies Plies other than face or back plies in a panel construction. Crossbands and centers are classed as inner plies (See Core).
Joint The common edge between two adjacent materials in the same plane.
Joint Edge Joint running parallel to grain of the wood.
Joint, Open Joint in which two adjacent pieces of veneer in the same plane do not fit tightly together (See Hairline).
Kerf The path that any saw makes in the process of cutting. Sawdust removed in the sawing process.
Kiln Drying Artificial method of dry lumber by forcing heated air to circulate around the lumber in an enclosed building.
Kiln Dried (KD) Wood that has been artificially dried to a moisture content required for a specific end-use application.
Knot A circular, woody fiber in a board that once formed the base of a branch or twig growing from the trunk of living tree.
Knots, Conspicuous Pin Sound knots 1/4 inch or less in diameter containing dark centers.
Knots, Sound Tight Knots that are solid across their face and fixed by growth to retain their place.
Lap A condition where one piece of veneer in the same ply overlaps another piece.
LFE Low Formaldehyde Emission.
Lineal Feet (LIN.FT.) A board 1 foot in length, regardless of width or thickness.
Logging The process of cutting trees and moving the logs to the sawmill.
Loose Side In knife-cut veneer, that slide of the sheet that was in contact with the knife as the veneer was being cut, and containing cutting checks (lathe checks) because of the bending of the wood at the knife edge. The Loose side of veneer darkness more than the Tight Side when stained with a wood finish.
MBF Thousand board feet.
Medium Density Fiberboard (MDF) A panel or core product manufactured from wood fibers combined with a synthetic resin or other bonding system. MDF is manufactured with a minimum density of 31 Lbs. per cubic foot up to 55 Lbs. per cubic foot by the application of heat and pressure by a process in which the fiber bond is substantially created by the addition of adhesive.
Medullary Rays Radial vertical tissues, extending across the growth rings of a tree, that enable the transmission of sap and produce a decorative spotted figure in quarter-sawn boards (especially oak and sycamore).
Millwork Lumber that has been "manufactured" by being run through such mill machines as a planer, straight line rip and moulded to stock or custom profiles.
Mineral Content of Wood Percentage of moisture present wood; degree of dryness. The weight of the water contained in the wood, usually expressed in percentage of weight of the oven-dry wood (Oven-Dry weight refers to 100% dry weight....zero moisture content). 8% moisture content means that 8% of the total wood weight is water.
Natural When referring to color and matching, veneers containing any amount of sapwood and/or heartwood.
Net Tally Lumber measured after kiln drying...this is the board footage measurement you must require and demand. (See Shrinkage & Measurement of Hardwood)
Number One Common (#1 Common) An excellent NHLA grade for furniture manufacturers and cabinet shops. This grade requires a clear face cutting yield of 66.6% up to 83.3%.
Occasional A small number of characteristics that are arranged somewhat diversely within the panel face.
Old Growth Timber growing in, or harvested from a mature, naturally established forest. When the trees have grown most or all of their individual lives in active competition with their companions for sunlight and moisture. There is no such thing as "original growth." Trees are much like....with age and disease they die.
Oven-Dry Wood Wood dried to constant weight in an oven maintained at temperatures of 101°C to 105°C (214°F to 221°F). No moisture content.
Particleboard A panel or core product composed of small particles and wood fiber that are bonded together with synthetic resin adhesives in the presence of heat and pressure.
Pecky Pockets of disintegrated wood caused by localized decay, or wood areas with abrupt color change related to localized injury such as bird peck. Pecky is sometimes considered as a decorative effect, such as bird peck in Pecan and Hickory or pecky in Cypress.
Phloem The principle food-conducting tissue of the vascular plants. Phloem (Inner Bark) carries food made in the leaves down to the branches, trunk and roots.
Pitch A resinous, gummy substance in firs and pines. This is the resin in the bag a baseball pitcher utilizes.
Pitch Pockets Defects resulting from resin accumulated between the growth rings in softwoods.
Pith The small soft center core of a tree around which growth takes place. The Pith in hardwoods is usually a cavity (open) while the Pith in softwoods is usually sound.
Plain (Flat) Sawn Lumber sawn tangent to the tree's annual rings. Most lumber is Plain Sawn. Advantages in Plain Sawing:
  1. Less costly and wasteful, hence more available;
  2. Easier to kiln dry;
  3. Averages wider widths.
Plain-Sliced (Flat-Cut) Veneer sliced parallel to the pith of the log and approximately tangent to the growth rings to achieve flat-cut veneer. Plain-sliced veneer is cut using either a horizontal are vertical slicing machine or by the half-round method using a rotary lathe.
Plasticity The properly that describes a wood's ability to retain its shape when bent (Toughness).
Pleasing Matched (Plywood Term) A face containing components which provides a pleasing overall appearance. The grain of the various components need not be matched at the joints. Sharp color contrasts at the joints of the components are not permitted.
Plywood An assembly made of layers (plies) of veneer, or of veneer in combination with a solid core, joined with an adhesive. The grain of adjoining plies is usually laid at right angles and almost always an odd number of plies are used to obtain balanced construction.
Pulp Wood fibers, ground and suspended in water, from which paper is made. Note: Hardwood pulp makes the best paper.
Quarter-Sawn (Lumber Term) In commercial practice lumber cut with rings (see either end of board) at angle of 45° to straight up 90°...i.e., parallel or almost parallel with medullary ray. In Oak it produces spotted figure; in Mahogany a ribbon-stripe. Advantages in Quarter-Sawing: Shrinks, twists, cusps, and splits less.
Quarter-Sliced (Veneer Term) A straight grain appearance achieved through the process of quarter-slicing or through the use of veneer cut in any fashion that produces a straight grain effect., cut is radial to the pith to the extent that ray fleck is produced and the amount of fleck is not limited.
Radial Coincident with a radius, from the axis of the tree or log to the circumference. A radial section is a lengthwise section in a plane theat extends from pith to bark.
Random Matched (Mismatched) A panel having the face made up of specially selected dissimilar (in color and grain) veneer strips of the same species and generally V-grooved at the joints between strips to stimulate lumber planking.
Random Width and Length (RW & L) The fact that hardwoods are almost always offered in a random width and length assortment can present something of a mystery. One is inclined to wonder, "Why aren't Birch, Oak and Walnut produced in convenient dimension sizes and Pine, Redwood, and Fir?" Answer: Hardwood lumber is cut to yield the maximum of usable material and minimize waste. Both widths and lengths are, therefore, random and even the best grades allow occasional defects.
Rate of Growth The speed at which a tree increases in size. This may be measured radially in the trunk, or in the lumber cut from the trunk, or in the dimension of the crown or other tree part. One unit of measure in wood is in the number of annual rings (years of growth).
Repairs (Plywood Term) A patch, shim or filler material inserted and/or glued into veneer or a panel to achieve a sound surface.
Repairs, Blending (Plywood Term) Wood or filler insertions similar in color to adjacent wood so as to blend well.
Rift-Cut (Veneer Term) A straight grain appearance achieved through the process of cutting at a slight angle to the radial on the half-round stay log or through the use of veneer cut in any fashion that produces a straight grain with minimal ray fleck.
Rift Sawing (Lumber Term) Rift sawing is midway between quarter-sawing and plain-sawing. It offers the same figure consistency as quarter-sawing but develops a more subtle grain figure (no medullary ray effect).
Rotary Cut Veneer produced by centering the log in a lathe and turning it against a broad cutting knife which is set into the log at a slight angle.
Rough Cut (Plywood Term) Irregular shaped areas of generally uneven corrugation on the veneer, differing from the surrounding smooth veneer and occurring as the veneer is cut by the lathe or slicer.
Running Match The panel face is made from components running through the flitch consecutively. Any portion of a component left over from a face is used as the beginning component or leaf in starting the next panel.
Sapwood The lighter colored wood growing between the heartwood and bark.
Selects A NHLA Hardwood Grading Rule that parallels the FAS 1 Face grade with different minimum size board requirements. The kiln dried Selects minimum board size is 3½" x 6'. Most other FAS 1 Face rules apply.
Shake A lengthwise separation of the wood occurring before the timber is cut into lumber, usually resulting from violent storms or in felling the log.
Sharp Contrasts (Plywood Term) For purposes of this Standard, this term means that face veneer of lighter than average color shall not be joined at the edges with veneer of darker than average color and that two adjacent pieces of veneer shall not be widely dissimilar in grain, figure, and other natural character markings.
Sidebend A distortion of a board in which there is a deviation edgewide from a straight line placed from end to end of the board. Once referred to as "crooked."
Silica The chemical compound silicon dioxide which is present in some woods. It imparts a hardness to the wood and dulls the cutting edges of tools used in machining. Especially with Teak and some exotic species.
Slight (Plywood Term) Visible on observation, but does not interfere with the overall aesthetic appearance with consideration of the applicable grade of the panel.
Slip Matched Veneer sheets jointed side-by-side to convey a sense of repeating flitch figure. Most common in quarter-sliced and rift veneers.
Softwood The non-porous wood of and cone-bearing, needle-leaved tree, regardless of whether the wood is in fact hard or soft...pine, fir, hemlock, etc.
Solid Core (Plywood Term) Plywood panels in which all inner plies are grade J or better. Splits up to 1/8 inch are allowed.
Sound Cutting A cutting free from rot, pith, shake and wane. It will admit sound knots, bird pecks. stain streaks or pin, shot and spot worm holes.
Sound Knot A knot which is solid across its face, as hard as the surrounding wood and shows no indication of decay.
Specific Gravity The ratio of the weight of a body o the weight of an equal volume of water; relative density.
Splits Separations of wood fiber running parallel to the grain.
SPP Species (plural).
Square Foot An area 12" x 12" or the equivalent of 144 square inches without regard to thickness.
Stain Discoloration in lumber caused by decay, fungi, etc. Normally avoidable through proper handling in the cutting and drying stages. Also, a finishing substance for coloring wood.
Steamed This term refers to a special process in which the green lumber (usually Walnut or Cherry) is steamed in vats for the purpose of darkening sapwood to blend with heartwood color.
Stripe, Ribbon A grain pattern often seen in tropical hardwoods caused by the spiral growth formation in the tree trunk. Quarter-sawn.
Surface Check The separation of the wood fibers, producing small, shallow, length-wise separation of wood along the board's surface.
Surface Measure (SM) Measuring method used for hardwood grade inspection. Same as square footage, expressed as a whole number. Fractions of measurement over and under a half foot are expressed as whole number respectively....i.e., a Surface Measure of 6.75 feet is rounded up to 7' Surface Measure. Surface measure is always a whole number.
Tally A record of the number of pieces and footage by grade.
Tight Side In knife-cut-veneer, that side of the sheet that was farthest from the knife as the sheet was being cut and containing no cutting checks (lathe checks).
Tongue and Grooved (T & G) Tongued and grooved on sides of board so that the tongue edge of one board fits into the grooved edge of the next board.
Tongue and Grooved & End-Matched Tongue and grooved on both sides and at both ends of piece, as in Oak flooring.
Torn Grain A defect in which fibers below the dressed surface are torn by the planer.
Toughness The property that allows wood to bend without breaking (see Plasticity).
Twist Spiral warpage of a board. The board is no longer flat.
Veneer A thin sheet of wood, rotary cut, sliced, or sawn from a log or flitch from a thickness of 1/100" up to ¼".
Vertical Grain (VG) The grain on quarter-sawn boards in softwood lumber.
V-Grooved Narrow and shallow V or U shaped channels machined on the plywood face surface to achieve a decorative effect. V-grooving is most commonly encountered in mis-matched or random matched wall panels as the grooves fall on the edge joints of the pieces of veneer making the face appear as planking.
Vine Mark Bands of irregular grain running across or diagonally to the grain which are caused by the growth of climbing vines around the tree.
Wane The presence of bark, or the lack of wood from and causes.
Wainscot Short length (3' high) wall paneling.
Warp A generic term that includes all variations from a true plane surface....i.e., bow, sidebend, cup and twist.
W.H.A.D. Worm holes a defect.
W.H.N.D. Worm holes no defect.
Wood Filler (Plywood Term) An aggregate of resin and strands, shreds, for flour of wood which is used to fill openings in wood and provide a smooth, durable surface.
Wooly Grain (Woolliness, Fuzzy Grain) Wood surfaces having wood fibers frayed loose, rather than severed cleanly, at the surface; commonly encountered in machining tension wood.
Worm Holes Voids in the wood caused by the burrowing action of certain wood-infesting worms, which do not survive the kiln-drying process.
Worm Tracks Marks caused by various types of wood attacking larvae. Often appear as sound discolorations running with or across the grain in straight to wavy streaks. Sometimes referred to as "pith flecks" in certain species of maple, birch and other hardwoods because of a resemblance to the color of pith.
Xylem The sapwood that carries sap from the roots to the leaves.