ABSOLUTE HUMIDITY – The weight of water vapour per unit volume of year, usually expressed as grains/cu

ABSORPTION – The gain of free water by the cell cavities

ACCLIMATISATION – The procedure of placing wood flooring in the area where it is to be installed to enable it to acclimatise or adjust its moisture content to correspond with that of its surroundings. When acclimatising wood flooring, the boards should be separated in such a manner as to enable air to circulate around them.

ACROSS THE GRAIN – Generally perpendicular to the grain direction.

ADHESIVE – Any substance such as glue, resin, cement or paste capable of holding or joining materials. Please visit our Carver Section.

ABSORBED WATER – Same as Bound Water.

ADSORPTION – The gain of bound water by the cell wall from adjacent air.

ADULT WOOD – Wood produced after cambial cells have attained maximum dimensions.

ADVANCED DECAY – An older stage of decay readily recognized as wood that has become punky, soft & spongy, stringy, ringshaked, pitted or crumbly.

AGAINST THE GRAIN – Reference to cutting direction, as in planning a board surface, such that splitting ahead of the cutter follows the grain direction downward into the wood below the projected cutting surface. Also, generally perpendicular to the grain direction, across the grain.

AIR-DRIED – Having reached equilibrium with outdoor atmospheric humidity. When unspecified, 12% moisture content is the assumed value.

ALIFORM PARENCHYMA – As seen in cross grain, an arrangement of parenchyma cells grouped closely around pores and forming wing like lateral extensions.

ALLOWABLE STRESS – A lumber stress level published for design use and identified with species and grade description and use specification.

ALONG THE GRAIN – Generally parallel to the grain direction.

ANISOTROPIC – Not having the same properties in all directions.

ASSEMBLY TIME – The time elapsed between spreading adhesive on surfaces to be joined and application of pressure to the joint.

BACK – The poorer of the two faces of a panel of plywood or other composites.

BALANCED CONTRUCTION – Symmetrical construction of plywood or other composites having matching layers on both sides of the central plane so that changes in moisture content will not cause warp.

BARK – The tree tissue outside of the cambium, including inner and outer bark.

BASTARD GRAIN – Lumber-having growth rings that form angles of 30° to 60° with the faces.

BEAM – An elongated member usually supported horizontally and loaded perpendicular to its length.

BIRDS EYE – Small circular areas resembling bird’s eyes on the tangential surface of wood, formed by indented fibres.

BLEMISH – A defect or anything that mars the appearance of wood.

BLUE STAIN – A bluish or greyish discoloration of sapwood caused by the growth of certain dark coloured fungi on the surface and inside the wood.

BOARD FOOT – A unit of lumber measurement equivalent to a piece having nominal dimensions of 1 ft. by 12 in.

BOARDS – Lumber 2 in or more wide that is nominally less than 2 in thick.

BOLE – A tree stem or trunk large enough for conversion onto lumber or veneer.

BOLT – A short section of a tree trunk.

BOUND WATER – Water in wood below the saturation point.

BOW – A form of warp.

BRASHNESS – Brittleness in wood, characterized by abrupt failure rather than splintering, causes include reaction wood, juvenile wood, high temperature and extremes of growth rate.

BROKEN STRIPE – Ribbon figure in which the stripe effect is intermittent.

BROWN ROT – Decay caused by a type of fungus that attacks cellulose rather than lignin, leaving a brownish residue.

BURL – A hard, woody outgrowth on a tree, more or less rounded in form, usually resulting from the entwined growth of a cluster of adventitious buds.

CAMBIUM – The thin layer of living, meristematic cells between bark and wood, which, by cell division, forms new, bark and wood cells.

CASE HARDENING – A condition in dry lumber wherein residual drying stresses leave the outer layers under compression but the inner core is tension.

CAVITY – The void space of a cell enclosed by the cell wall.

CELL – The basic structural unit of wood tissue consisting of an outer cell wall surrounding a central cavity or lumen.

CELLULOSE – A polymer chain carbohydrate, the major constituent of wood cell walls.

CHECKS – Separations of wood cells along the grain as a result of uneven shrinkage, most common end grain surfaces of lumber.

CHIPPED GRAIN – A machining defect in which small chips are torn from the surface below the intended plane of cut, usually as the result of cutting against the grain.

CLEAR – In reference to lumber, free of defects or blemishes.

CLEARANCE ANGLE – The angle between the back of the knife and the path of the cutting edge.

CLOSE GRAIN – Slowly grown wood having narrow, usually inconspicuous growth rings in contrast to coarse grain or open grain.

CLOSED FACE – Same as closed side.

CLOSED GRAIN – See Fine Texture.

CLOSED SIDE – The veneer surface not touching the veneer knife during peeling or slicing, which is free of knife checks.

COARSE GRAIN – Descriptive of wood having wide and conspicuous growth rings in contrast to close grain.

COARSE TEXTURE – Descriptive of wood having relatively large pores, especially in reference to finishing.

COLLAPSE – A shrivelled or irregular appearance of wood due to flattened or caved-in cell structure, usually caused by capillary tension during early stages of drying wet wood.

COMPRESSION FAILURES – Irregular planes of buckled cells, caused by excessive compressive stress parallel to the grain, appearing as fine cross wrinkles on longitudinal planed surfaces.

COMPRESSION WOOD – See Reaction Wood.

CONDITIONING – Exposure under controlled relative humidity to bring wood to desired moisture content. Also, the final stage of kiln schedule designed to relieve residual casehardening stress.

CONFLUENT PARENCHYMA – As seen in cross section, parenchyma cells so grouped to form a more or less tangential band connecting two or more pores.

CONIFEROUS WOOD – Same as Softwood.

CORD – A unit of measure for round-wood, such as firewood and pulpwood.

CORE – The inner portion of a board, equivalent to half its thickness.

CORE WOOD – Same as Juvenile Wood.

CRACK – A large radial check resulting from greater tangential than radial shrinkage.

CREEP – Time-dependent deformation of a wood member or adhesive joint due to sustained stress.

CROOK – A form of warp.

CROSSBANDS – In plywood with more than three piles, those veneers immediately beneath the faces, having grain direction perpendicular to that of the faces.

CROSS-BREAKS – Transverse planes of failure in tension parallel to the grain, caused by localized abnormal longitudinal shrinkage restrained by adjacent normal wood.

CROSS GRAIN – Deviation of grain direction from the longitudinal axis of a piece of wood from the stem axis in a tree.

CROSS SECTION – A section cut perpendicular to the grain, or the surface exposed by such a cut.

CROTCH GRAIN – Figure produced by cutting centrally through a tree crotch in the common plane of both branches.

CUP – A form of warp.

CURING – The setting of an adhesive by chemical reaction. Also, the drying of wood, though this is not preferred usage.

CURLY FIGURE – Same as wavy grain.

CUTTING ANGLE – The angle between the face of a cutting angle and a plane perpendicular to its cutting direction.

DECAY (ROT) – The decomposition of wood by fungi.

DECIDUOUD TREES – Trees whose leaves normally drop after the yearly period of growth is over.

DEFECTS – Irregularities or abnormalities in wood that lower its strength, grade, value or utility.

DELAMINATION – The separation of layers in laminated wood or plywood caused by the failure of the adhesive itself or the interface between adhesive and adhered.

DENSE GRAIN – Same as Close Grain.

DESNSITY – The weight of a body or substance per unit volume.

DESORPTION – The loss of bound water from the cell wall.

DEWPOINT – The temperature at which atmospheric water vapour condenses out as a liquid.

DIAGONAL GRAIN – Cross grain exhibiting deviation of the growth ring plane from the longitudinal axis, commonly the result of sawing boards other than parallel to the back of the log.

DIAMONDING – A form of warp resulting from greater tangential than radial shrinkage, which causes square sections to become diamond shaped or round sections to become oval.

DICOTS – A class of plants characterized by having two cotyledons or seed leaves.

DIFFUSE-POROUS WOOD – A hardwood in which the pores are approximately uniform size and are distributed evenly throughout each growth ring.

DIMENSIONAL STABILIZATION – Treatment of wood to minimize shrinkage and swelling.

DIMPLES – Numerous small depressions in growth rings, especially obvious on split tangential surfaces. Occasionally occurs among certain conifers, notably ponderosa and lodgepole pines.

DIP GRAINED – Having a single wave or undulation of fibre direction, such as occurs in wood along either side of a knot.

DRESSED SIZE – The dimensions of lumber after being surfaced with a planning machine.

DRY BULB TEMPERATURE – The temperature of the air is indicated by a standard thermometer.

DRYING DEFECTS – Irregularities resulting from drying that may lower the strength, durability or utility of wood, such as checks or casehardening.

DRY KILN – Same as Kiln.

DRY ROT – A term loosely applied to any dry, crumbly rot, but especially to that which, when in an advanced state, permits the wood to be crushed easily to dry powder. The term is actually a misnomer for any decay, since all fungi require considerable moisture for growth.

DURABILITY – A general term referring to resistance to deterioration; frequently refers specifically to decay resistance of wood, but also in resistance of adhesive bonds and finishes to deterioration.

EARLY WOOD – The first formed portion of the growth ring, often characterized by larger cells and lower density.

EDGE GRAIN – Referring to pieces in which the growth rings form an angle of 45° or more (ideally 90°) with the wood surface or lumber face; approaching or coinciding with a radial surface.

ELASTICITY – A property of material meters that contact or penetrate the wood when measuring moisture content.

ELECTRODES – Components of moisture meters that contact or penetrate the wood when measuring moisture content.

ELEMENT – Same as cell.

ENCASED KNOT – The dead portion of a branch embedded in the stem by subsequent growth of the tree.

END GRAIN – A cross sectional surface or the appearance of such a surface.

EQUILIBRIUM MOISTURE CONTENT (EMC) – The moisture content eventually attained in wood exposed to a given level of relative humidity and temperature.

EVEN GRAIN – Wood having uniform or nearly uniform structure throughout the growth ring and little or no earlywood distinction, as in basswood.

EXTRACTIVES – Substances deposited in wood in the transition from sapwood to heartwood, often imparting significant colour and decay resistance.

FACE – Either side or surface of a plywood panel.

FACE GRAIN – The figure or pattern on the face side of a plywood panel or board.

FACTORY AND SHOP LUMBER – Lumber intended to be cut up for use in further manufacture.

FEATHER CROTCH – The figure produced by a longitudinal section through a tree crotch, characterized by a feather like appearance.

FIBER – A specific hardwood cell type typically elongated with pointed ends, having thick walls and contributing notably to the strength of wood. Also, in the plural, used as a general term for separated wood cells collectively, as in paper making.

FIBER BOARD – A panel product manufactured or refined or partially refined wood fibres.

FIBER SATURATION POINT (FSP) – The condition of moisture content where cell walls are fully saturated but cell cavities are empty of free water.

FIGURE – Any distinctive appearance on a longitudinal wood surface resulting from anatomical structure, irregular coloration or defects.

FINE GRAIN – See close grain. Also, sometimes used synonymously with “fine texture” to designate woods with relatively small cells.

FINE TEXTURE – Descriptive of hardwoods having small and closely spaced pores, or softwoods with small diameter tracheids. Preferred to “closed grain” in reference to finishing.

FLAME GRAIN – Applied to figure produced on flatstone boards or rotary cut veneer.

FLATSAWN – Indicating wood machined along an approximately tangential plane, such that growth rings intersect the surface at an angle of less than 45°.

FLITCH – A portion of a log sawn on two or more faces, commonly on opposite faces, leaving two waney edges. When intended for re-sawing into lumber, it is re-sawn perpendicular 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.

FLUORESCENCE – The absorption of ultraviolet light by a material that transforms the energy and emits it as a visible light of a particular colour.

FREE WATER – Moisture held in the cell cavities of the wood, not bound in the cell wall.

FUNGI – Simple forms of microscopic plants, whose parasitic development in wood may cause mould, stain or decay.

FUZZY GRAIN – See Woolly grain.

GELATINOUS FIBERS – Fibres in hardwoods with abnormal inner cell walls, associated with tension wood.

GRADE – A designation of the quality of a log, or of a wood product such as lumber, veneer or panels.

GRAIN – A confusingly versatile term whose specific meaning must be made apparent by context or by associated adjectives.

GRAIN DIRECTION – The direction of the long axes of the dominant longitudinal cells or fibres in a piece of wood.

GRAINING – Painting or otherwise imitating the figure of wood on a surface.

GRAIN SLOPE – See sloping grain.

GREEN – Freshly cut and unseasoned. Also, having moisture content above fibre saturation point.

GROSS FEATURES – Physical features of wood that can be perceived with the unaided eye, sometimes including macroscopic features.

GROWTH RING – The layer of wood added to the stem in a given growth period; in the temperate zones, one layer is added per yearly growth period and is often termed annual ring.

GYNOSPERM – The class of plants having naked seeds. Within this group are all yielding softwood trees.

HAND LENS – A magnifying lens, hand held, used to examine wood.

HARDNESS – The property of wood that measures its resistance to indentation.

HARDWOOD (POROUS WOOD) – Woods produced by broad-leaved trees in the botanical group referred to as angiosperms. Since these woods have vessels, they are also termed porous woods, because a vessel in cross section is termed a pore.

HEADSHAW – The principal breakdown machine in a sawmill, usually either a circular saw or a bandsaw.

HEART SHAKE – Radial crack in the vicinity of the pith.

HEARTWOOD – The central core of wood in mature stems. At one time heartwood was sapwood but it no longer conducts sap or has living cells. In most species, extractives impart a darker colour to heartwood.

HONEYCOMBING – Checks that occur in the interior of a piece of wood, usually in the plane of the rays, as a result of case-hardening stresses developed in drying.

HOOK ANGLE – Same as cutting angle.

HOOKE’S LAW – A law that states for elastic materials, strain is proportional to stress within the elastic range.

HYDROMETER – An elongated, weighted glass instrument that measures the specific gravity of liquid. Used by woodworkers to determine the strength of PEG solutions.

HYGROMETER – An instrument that measures the relative humidity of the atmosphere.

HYGROSCOPICITY – The ability of a substance to adsorb and desorb water.

HYDROSCOPIC WATER – Same as bound water.

HYPHAE – The microscopic filaments of a fungus, which digest and adsorb material from its host.

INCIPIENT DECAY – An early stage of decay in which hyphae have invaded the cell structure, sometimes discolouring the wood, but have not perceptibly reduced the hardness of the wood.

INCREMENT – The growth added in a given period.

INNER BARK – See bark.

INTERGROWN KNOT – A portion of a branch that was alive then intergrown with the surrounding stem.

JOIST – One of a series of parallel beams used to support floor and ceiling loads, usually installed with its wide dimension vertical. See also Plank.

JUVENILE WOOD (CORE WOOD, PITH WOOD) – Wood formed near the pit of the tree, often characterized by wide growth rings of lower density and abnormal properties, See also Adult Wood.

KILN (DRY KILN) – A heated chamber for drying lumber, veneer, and other wood products, in which temperature, humidity, and air circulation are controlled.

KILN-DIRED – Having been dried in a kiln to a specific moisture content; for cabinet woods, usually implies dryness below that attainable by air-drying. See also Air-Dried.

KILN SCHEDUAL – A sequence of dry-bulb and wet-bulb temperatures specified for successive stages of drying lumber in a kiln, designed to attain desired dryness without defects.

KINK – A form of warp characterized by abrupt deviation from straightness or flatness due to either localized grain distortion (as around knots) or to deformation by misplaced stickers.

KNIFE CHECKS (LATHE CHECKS) – Parallel-to-grain failures developed cyclically in one side of knife cut veneer during its manufacture: depth of checks varies with species and cutting conditions. Also, called lathe checks, especially in peeled veneer. See also Closed Side, Open Side.

KNOT – A portion of a branch overgrown by the expanding girth of a bole or a larger branch. See also Intergrown Knot, Encased Knot, Spike Knot, Pin Knot.

LAMINATED VENEER LUMBER (LVL) – A structural lumber manufactured from veneers with the veneer running parallel to each other.

LATEWOOD (SUMMERWOOD) – The portion of growth ring formed after earlywood, often characterized by smaller cells or higher density.

LATHE CHEAKS – See Knife Checks.

LEAF GRAIN – Another term for flat-grain figure.

LIGNIN – A complex chemical substance making up approximately 25% of wood substance, interspersed with cellulose in forming the cell wall. Lignin stiffens the cell and functions as a bonding agent between cells.

LONGITUDINAL – Parallel to the stems axis of the tree or branches, therefore describing the axial direction of the dominant cell structure; along the grain.

LONGITUDINAL GRAIN – Any plane cut parallel to the grain direction of wood. It may be radial, tangential, or an intermediate plane.

LOOSE KNOT – See Encased Knot.

LOOSENED GRAIN 9SHELLED GRAIN) – Separation of latewood layers from a planed surface, usually accompanying pronounced raised grain and typically occurring on the pith side of flat sawn boards.

LOOSE SIDE – Same as Open Side.

LUMBER – Pieces of wood no further manufactured than by sawing, planning, crosscutting to length, and perhaps edge-matching.

LUMEN (CELL LUMEN) – See Cavity.

MACROSCOPIC – referring to features visible with low-power magnification (e.g., a 10x hand lens), as distinguished from microscopic features.

MATURE WOOD – See Adult Wood.

MEDULLA – See Pith.

MEDULLARY RAYS – Rays connected with the pith. Often used (loosely) to refer to all rays.

MERISTEM – Reproductive tissue. Apical meristems are located in twig tips and produce elongation. The cambium is a lateral meristem producing girth.

MICROBEVEL – An extremely narrow bevel along a cutting edge, which increases the sharpness angle for greater edge durability.

MICROMETER (mm) – 1/1000 of a millimetre, or approximately 1/25,000 of an inch.

MIL – 1/1000 of an inch.

MIXED GRAIN – Referring to a quality of lumber containing both edge-grain and flat-grain pieces.

MODULUS OF ELASTICITY – The ratio of stress to strain, within the elastic range of material

MODULUS OF RUPTURE – In reference to wood, the stress in bending sustained at failure.

MOISTURE CONTENT – The weight of water in the cell walls and cavities of wood, expressed as a percentage of oven-dry weight.

MOISTURE GRADIENT – The variation of moisture content in wood, such as the graduation from wetter core to drier surface in a drying board.

MOISTURE METER – an instrument used for the rapid determination of moisture content in wood by electric means.

MOLD – A fungal growth on wood taking place at or near the surface, usually greenish to black in colour.

MONOCOTS (MONOCOTYLEDONS) – A class of plants (within the angiosperms) characterized by a single cotyledon or seed leaf. See also Dicots.

MOTTLED FIGURE – A type of broken stripe figure having irregular interruptions of curly figure.

MYCELIUM – The mass of hyphae (microscopic elements) of a fungus, often visible as a cottony mat or layer on the surface of wood with advanced decay.

NARROW GARIN – Same as Close Grain.

NEEDLE-POINT GRAIN – Same as Rift Grain.

NOMINAL DIMENSION – The dimension by which lumber is known and sold in the market (the actual dimension after drying and dressing may be somewhat less)

NONPOROUS WOOD – See Softwood.

OLD GROWTH (VIRGIN TIMBER) – Trees in a mature, naturally established forest, whose timber is characterized by large size, straight holes and freedom from knots.

OPEN ASSEMBLY TIME – See Assembly Time.

OPEN FACE – Same as Open Side.

OPEN GRAIN – See Corse Texture. Also, descriptive of wood having widely spaced growth rings, in contrast to close or dense grain.

OPEN PILING – Stacking wood products in layers separated by stickers to permit air circulation.

OPEN SIDE (LOOSE SIDE, OPEN FACE) – The surface of veneer against the knife during peeling or slicing; may contain knife checks.

ORIENTED STRANDBOARD (OSB) – A type of panel product made from strand-like flakes that are aligned in directions that improve the properties of the panel in the alignment directions over panels with random flake orientation.

OUTER BARK – See Bark.

OUTER WOOD – Same as Adult Wood.

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)

OVERLAY – Sheet materials other than veneer (plastics, paper, and metal) glued to the surface of wood panels.

PARENCHYMA – Thin-walled wood cells (living when part of sapwood) involved mainly with food storage and distribution. With a hand lens, groupings of parenchyma may appear as light-coloured areas on cross sections. See also Prosenchyma.

PECK (PECKINESS, PECKY DRY ROT) – Advanced decay in living trees that occurs in the form of elongated pockets of rot; most familiar in bald cypress and incense cedar.

PEELED VENEER – Same as Rotary.

PHLOEM – The tissue of the inner bark, which conducts food in the tree. Also used loosely in reference to bark in general.

PIGMENT FIGURE – Figure in wood resulting from irregular deposits of coloured extractives.

PINHOLES – Small round holes in wood caused by insects.

PIN KNOT – a knot less than ¼ in. in diameter.

PITCH – Material formed in the resin canals of softwood; also, accumulation of resin, as in pockets, streaks, or seams, or as is exuded from wounds.

PITCH POCKET – A flattened round or oval tangential separation in the wood of conifers, which contains (or did contain) solid or liquid resin (pitch)

PITH (MEDULLA) – The small core of soft, spongy tissue located at the centre of tree stems, branches, and twigs.

PITH FLECKS – Longitudinal streaks of wound tissue caused by the vertical tunnelling of fly larvae belonging to the genus Agromyza.

PITH WOOD – Same as Juvenile Wood.

PITS – Recesses or un-thickened portions of the secondary cell walls through which fluid pass from cell to cell.

PLAINSAWN (PLAIN GRAIN) – Same as Flat-sawn.

PLANK – A piece of structural lumber installed with its wide dimension horizontal, usually intended as a bearing surface. See also Joist.

PLYWOOD – A composite board of veneers glued together with the grain direction of adjacent layers mutually perpendicular.

POCKET ROT – A localized, sharply delineated volume or pocket of advanced decay surrounded by apparently sound wood.

PORE – The cross section of a hardwood vessel.

PORE MULTIPLE – Two or more pores arranged radically and in close contact.

POTOUS WOOD – Same as Hardwood.

POT LIFE – Same as Working life.

POWER_POST BEETLES – Small beetles, especially of the genus Lyctus, which attack mainly sapwood of large-pored hardwoods, reducing the tunnelled wood to fine power.

PRESERVATIVE – Any substance used to treat wood for the protection against fungi, insects, or marine borers.

PROSENCHYMA – Non-living wood cells that function in conduction and support. Includes tracheids, vessels, and fibres and accounts for most of the volume of wood structure. See also Parenchyma.

PSYCHROMETER – a type of hygrometer for measuring atmospheric humidity by dry-blub and wet-blub thermometers.


QUILTED FIGURE – Figure sometimes found in big leaf maple, characterized by crowded bulges in the grain direction.

RADIAL – The horizontal direction in a tree between pith and bark. A radial section is along a plane that would pass lengthwise through pith.


RAISED GRAIN – A condition developed in planning causing the elevation of latewood above earlywood, without separation, typically on the pith side of flat-sawn boards. Also, several cells caused to rise above a surface by intentional wetting, as done in preparation for final sanding.

RAKE ANGLE – See Cutting Angle.

RATE OF GROWTH – The relative rate of increase in tree girth, usually expressed as rings per inch.

RAY FLECKS – The conspicuous appearance of rays on an edge-grain surface.

RAYS – Flattened bands of tissue composed of ray cells, extending horizontally in a radial plane through the tree stem. See also Medullary Ray.

REACTION WOOD – Abnormal wood formed in leaning stems and branches in trees. In softwood trees, it forms on the lower side of the stem and is called compression wood; it is denser but more brittle and has greater than normal longitude shrinkage. In hardwood trees, reaction wood forms typically on the upper side of the stem and is termed tension wood, characterized by woolly surfaces when machined and greater than normal longitudinal shrinkage.

RED KNOT – See Intergrown Knot.

RELATIVE HUMIDITY – The ratio of the amount of water vapour present in the air to that which the air would not hold at saturation at the same temperature. Usually expressed as a percentage. See also Absolute Humidity.

RESIN – Material secreted into resin canals of softwood trees. Also, a term applied to certain synthetic organic products (as used in glues and finishes) similar to natural resins. See also Pitch.

RESIN CANAL – Tubular passageways containing resin in the wood of certain softwood trees.

RIBBON FIGURE (RIBBON GRAIN, STRIPE FIGURE) – Figure apparent on an edge-grain surface of wood with interlocked grain, characterized by vertical bands of varying lustre and vessel markings. See also Broken Stripe.

RIFT CRACK – See Heart Shake.

RIFT GRAIN (COMB GRAIN, NEEDLE-POINT GRAIN) – The surface or figure produced by a longitudinal plane of cut, which is at approximately 45° to both rays and growth rings. The term is used especially for white oak with its large rays. The term comb grain is used where the vessel lines are parallel to the board edge and the rays produce a uniform pencil stripe.

RING-POROUS WOOD – Hardwood having relatively large pores concentrated in earlywood and distinctly smaller pores in latewood. See also Diffuse-Porous Wood.

RING SHAKE (RING FAILURE. SHELL SHAKE) – A separation of wood structure parallel to the growth rings, often in the first layer(s) of earlywood, usually occurring in the standing tree.

RIPPLE MARKS – Fine striations perpendicular to the grain, most apparent on a tangential surface, produced in wood with storied rays.

ROE FIGURE (ROEY GRAIN) – The appearance of a radial surface when stripes less than 1ft. long are formed by irregular interlocked grain.

ROT – See Decay.

ROTARY-CUT BENEER (PEELED VENEER) – Veneer cut on a lathe by rotating a log fixed against a knife, which produces a continuous veneer sheet.

ROUND-EDGE LUMBER – Lumber-having bark along both edges.

ROUND KNOT – The round or oval exposed section of a knot cut more or less crosswise to the limb axis. See also Spike Knot.

SAP – The water in a tree, including any dissolved nutrients and extractives.

SAPSTAIN – See Blue Stain.

SAPWOOD – The physiologically active wood comprising one to many outermost growth rings, usually lighter in colour than heartwood.

SEASONING (CURING) – the process of drying wood.

SECOND GROWTH – Timber that has grown in an area following harvest or destruction of previous timber.

SELECT – In softwood lumber, the highest appearance grades are Select grades, usually separated as B and better, C, and D Select grades. In hardwood factory lumber, Selects is one specific grade, placing in quality below Firsts and Seconds, but higher than Common grades.

SEMI-DIFFUSE POROUS WOOD (SEMI-RING-POROUS WOOD) – Hardwood having fairly even distributed pores of gradually decreasing size form earlywood to latewood portions of the growth ring.

SHAKE – See Ring Shake, Heart Shake. Also, a hand-split shingle.

SHARPNESS ANGLE – The angle between the face and the back of a cutting edge, usually designated by the Greek letter b.

SHEAR – A condition of stress (and resulting strain) acting to cause portions of an object to move or slide in parallel but opposite direction from one another.

SHELL – The outer portion of a board, equivalent to one-quarter the thickness. See also Core

SHELLED Grain – See Loosened Grain.

SHELL SHANK – See Ring Shank.

SHORT GRAIN – See Cross Grain.

SHORT IN THE GRAIN – Term sometime used to describe brittle fractures in wood.

SHRINKAGE – Change in dimension due to loss of moisture below the fibre saturation point, expressed numerically as a percentage of green dimension.

SIDE GRAIN (SIDE CUT) – Same as Flat-sawn. Also, any longitudinal surface, as opposed to end grain.

SILVER GRAIN – Figure produced by showy or lustrous ray fleck on a quartered surface.

SLAB – A broad, flat, thick, piece of wood. Also, a surface cut from a log with bark on one side.

SLASH GRAIN (SLASH SAWN) – Same as Flat-sawn.

SLICED VENEER – Veneer produced by moving a log or flitch vertically against a fixed veneer knife.

SLOPE OF GRAIN (GRAIN SLOPE) – a measurement of cross grain taken as the amount of grain deviation across a board in a measured distance along its length, expressed as a ratio such as 1 in. in 12 in., or 1 in 12, or simply 1:12.

SOFT ROT – A type of decay that develops under very wet conditions, as in docks or boat timbers, caused by fungi that attack the interior of the secondary cell wall.

SOFTWOOD (CONIFEROUS WOOD) – Wood produced by coniferous trees in the botanical group referred to as gymnosperms. Since these woods lack vassals, they are sometimes referred to as nonporous woods. (The term softwood does not necessarily refer to the actual hardness of the wood)

SOLID PILING (BULK PILING) – Close stacking of lumbers or other products, without separation of layers with stickers, as in open piling.

SOLITARY PORE – Pores that do not touch other pores are surrounded completely by other types of cells as seen in cross section.

SOUND KNOT – A knot that is solid throughout and shows no signs of decay.

SOUND WOOD – Wood having no decay.

SPALTED WOOD – Partially decayed wood characterized by irregular discolorations appearing as dark zone lines on the surface.

SPECIFIC GRAVITY – The ratio of the weight of a body to the weight of an equal volume of water, relative density.

SPIKE KNOT – A knot cut more or less parallel to its long axis so that the exposed section is definitely elongated. See also Round Knot.

SPIRAL GRAIN – Cross grain indicated by grain deviation from the edge of a tangential surface, resulting naturally from helical grain direction in a tree or artificially by misaligned sawing.

SPRINGWOOD – Same as Earlywood.

STAIN – A discoloration in wood caused by stain fungi, metals, or chemicals. Also, a finishing material used intentionally to change the colour of the wood.

STAR SHAKES (STAR CHECK) – Multiple heart shake, having more or less star effect.

STARVED JOINT – poorly bonded glue joint, due to insufficient glue.

STATIC BENDING – Bending under a constant load or slowly applied load.

STEEP GRAIN – Rather severe cross grain.

STICKERS – Wooden strips used to separate layers of lumber to permit air circulation.

STORIED RAYS – Rays whose arrangement (as viewed on a tangential section) is in horizontal rows. See also Ripple Marks.

STRAIGHT BANDS – Internal piles of plywood, other than the core ply, having grain direction parallel to that of the face piles.

STRAIGHT GRAIN – Indicating grain direction parallel to the axis or edges of a piece.

STRAIN – Unit deformation resulting from applied stress.

STRENGHT – The ability of wood to resist applied load.

STRESS – The force or load per unit area resulting from external loads as in a structure, or internal conditions as in drying.

STRIPE FIGURE (STRIPE GRAIN) – Same as Ribbon Figure.

SUMMERWOOD – See Latewood.

SUNKEN JOINT – A depression at a glue joint resulting from surfacing edge-glued material too soon after gluing.

SURFACE CHECKS – Checks that develop on a side-grain surface and penetrate the interior to some extent.

SWELLING – Increase in the dimensions of wood due to increase in moisture content.

TANGENTIAL – Describing surfaces and sections of wood perpendicular to the rays and more or less parallel to the growth ring.

TANGENTIAL CUT – See Flat-sawn.

TENSION WOOD – See Reaction Wood.

TERMINAL PARENCHYMA – Parenchyma cells located at the end of the growth ring, sometimes forming a conspicuous light line delineating the growth ring, as in yellow-popper.

TEXTURE – Relative cell size indicated by adjectives from fine to coarse; in softwoods, determined by relative pore diameter. Also, sometimes used to indicate evenness of grain, e.g. “Uniform texture” and uniformity in size and distribution of pored, e.g., even texture. See also Coarse Texture, Fine Texture.

THERMAL CONDUCTIVITY – The transfer of heat through a material by conduction; the K factor indicates the relative rate of thermal conductivity. The lower the K factor, the better the insulating properties and the poorer the conducting properties.

THERMAL EXPANSION – The increase in dimension of a material in response to increase in temperature.

TIGER GRAIN – Same as Curly Figure.

TIGHT KNOT – Same as Intergrown Knot.

TIGHT SIDE – Same as Closed Side.

TIMBER – Wood in standing trees having potential for lumber.

TISSUE – A group or mass of cells having similar function or a common origin.

TORN GRAIN – Same as chipped grain. Also, in plywood or veneer, a growth ring separation.

TRACHEIDS – Elongated conductive cells comprising more that 90% of softwood tissue; also found in some hardwoods.


TRUNK – The main stem of a tree. See also Bole.

TWIST – A form of warm in which the four corners of a flat face are no longer in the same plane.

TYLOSES – Bubble-like structures that form in certain vassals of hardwood, usually in conjunction with heartwood formation.

TYLOSOIDS – Bubble-like structures that form in the resin of certain softwood.

UNEVEN GRAIN – Wood with growth rings exhibiting pronounced differences in appearance between earlywood and latewood, as in southern yellow pine or white ash.

VASICENTRIC PARENCHYMA – Parenchyma that forms a complete sheath one to many cells thick around a vessel.

VENEER – Wood cut by slicing, peeling, or sawing into sheets ¼ in. or less in thickness.

VERTICAL GRAIN – Same as Edged Grain.

VESSEL – A conductive tube in hardwoods formed by end-to-end arrangement of cells whose end walls are open. The cross section of a vessel is called a pore.

VESSEL LINES – In hardwoods with a fairly large diameter vessel, the visible lines produced on longitudinal surfaces wherever the plane of cut opens vessels lengthwise.


WAFTERBOARD – A panel product made of wafer-type flakes and having equal properties in all directions parallel to the surface of the panel.

WANE – Bark, or lack of wood from any cause, on the edge or corner of a piece of lumber.

WARP – Distortion of the intended shape of a piece of wood. See also Bow, Crook, Cup, Diamonding, Kink, and Twist.

WAVY BANDS OF PORES – Pores arranged in undulating bands approximately parallel to the growth rings, as in the latewood of elm and hackberry.

WAVY GRAIN (CURLY GRAIN) – Undulations of the grain direction creating horizontal corrugations on a radially (and sometimes tangentially) split surface.

WEATHERING – Discoloration and disintegration of wood surfaces due to environmental influences such as wind, dust, abrasion, light, and variations in precipitation and humidity.

WET-BULB DEPRESSION – The difference between dry-blub and wet-blub temperatures.

WET-BULB TEMPERATURE – The temperature as measured by a thermometer whose bulb is covered in water-saturated cloth, the evaporation form which lowers the temperature in relation to the relative humidity of the air.

WHITE ROT – Decay caused by a type of fungus that leaves a whitish spongy or stingy residue, See also Brow Rot.

WHORL – In coniferous trees, a group of branches that occurs at regular intervals or nodes along the main stem.

WITH THE GRAIN – Reference to cutting direction, in planing a board surface, such that splitting ahead of the cutter follows the grain direction upward and out of the projected surface. See also Against the Grain.

WOOD (XYLEM) – The cellular tissue of the tree (exclusive of pith) inside the cambium.

WOOD SUBSTANCE – The solid material of which wood is composed, principally cellulose and lignin, exclusive of extractives and sap.

WOOLLY GRAIN (WOLLINESS< FUZZY GRAIN) – Wood surfaces having wood fibres frayed loose, rather than severed cleanly, at the surface; commonly encountered in machining tension wood.

WORKING LIFE (POT LIFE) – The period of time after mixing during which an adhesive remains usable.

X – Symbol for cross section or cross-sectional surface.

XYLEM – Same as Wood.

ZONE LINES – See Spalted Wood.

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