**Asthenosphere** – the highly viscous, mechanically weak and ductilely-deforming region of the upper mantle of the Earth. It lies below the lithosphere, at depths between 100 and 200 km (~ 62 and 124 miles) below the surface, but perhaps extending as deep as 700 km (~ 435 miles).

**Aflockalypse** – a portmanteau of the words “flock” and “apocalypse”, referring to the mass bird deaths of 2010~2011 (adopted by certain media commentators).

**Atmosphere (unit)** – an international reference pressure defined as 101,325 Pascals and formerly used as unit of pressure. For practical purposes it has been replaced by the bar which is 100,000 Pascals. (The 1% difference is negligible.)

**Bending** – characterizes the behavior of a slender structural element subjected to an external load applied perpendicularly to a longitudinal axis of the element.

**Bollard** – a thick, low post, usually of iron or steel, mounted on a wharf or the like, to which mooring lines from vessels are attached.

**Brute force** – One of various methods used to unnaturally force a warped piece of wood into a straight or otherwise desired position via an applied mechanical advantage.

**Bulk modulus** – a measure of a substance’s resistance to uniform compression, defined as the pressure increase needed to decrease the volume by a factor of 1/e, or about 0.368. Its base unit is the pascal.

**Calcite** – one of the commonest minerals, calcium carbonate, CaCO_{3}, found in a great variety of crystalline forms: a major constituent of limestone, marble, and chalk.

**Capacity factor** – the average expected output of a generator, usually over an annual period. Expressed as a percentage of the nameplate capacity (full-load or maximum output) or in decimal form (e.g. 30% or 0.30).

**Capillary action** – the ability of a liquid to flow against gravity where liquid spontaneously rises in a narrow space such as a thin tube, or in porous materials such as paper or in some non-porous materials such as liquified carbon fibre.

**Carbon footprint** – a measure of the amount of carbon dioxide produced by a person, organization, or location at a given time.

**Carbon nanotube** – allotropes of carbon with a cylindrical nanostructure. Nanotubes have been constructed with length-to-diameter ratio of up to 132,000,000:1, significantly larger than for any other material. These cylindrical carbon molecules have unusual properties, which are valuable for nanotechnology, electronics, optics and other fields of materials science and technology.

**Catastrophic failure** – a sudden and complete failure of a system from which recovery is impossible.

**Catenary** – the curve that an idealised hanging chain or cable assumes when supported at its ends and acted on only by its own weight.

**Collet** – a slotted cylindrical clamp inserted tightly into the tapered interior of a sleeve or chuck on a lathe to hold a cylindrical piece of work.

**Column** – a vertical structural element that transmits the load above to the structural elements below.

**Common terminal** – one of three electrically active terminals on a 3-way switch that bridges the power supply and the load (light fixture). Toggling the switch connects the common terminal to one of the two remaining terminals while disconnecting from the other.

**Copenhagen interpretation** – holds that quantum mechanics does not yield a description of an objective reality but deals only with probabilities of observing, or measuring, various aspects of energy quanta, entities which fit neither the classical idea of particles nor the classical idea of waves.

**Creep** – the tendency of a solid material to slowly move or deform permanently under the influence of stresses.

**Cross section** – a section made by a plane cutting anything transversely, esp. at right angles to the longest axis.

**Cullet** – Glass that is crushed and ready for recycling via remelting.

**Curtain wall** – an outer covering of a building in which the outer walls are non-structural, but merely keep the weather out and the occupants in. The curtain wall facade does not carry any dead load weight from the building other than its own dead load weight.

**Degree of freedom** – the set of independent displacements and/or rotations that specify completely the displaced or deformed position and orientation of the body or system.

**Density** – the ratio of mass per unit volume, typically kg/m^{3}. It is mathematically defined as *p*=*m*/V, where *p* is the density, *m* is mass, and V is the volume.

**Derivative** – The derivative of a function of a real variable measures the sensitivity to change of a quantity. For example, the derivative of the position of a moving object with respect to time is the object’s velocity. The derivative of a function of a single variable at a chosen input value, when it exists, is the slope of the tangent line to the graph of the function at that point. The tangent line is the best linear approximation of the function near that input value. For this reason, the derivative is often described as the “instantaneous rate of change”, the ratio of the instantaneous change in the dependent variable to that of the independent variable.

**Elasticity** – the physical property of a material that returns to its original shape after the stress (e.g. external forces) that made it deform is removed.

**Elastic modulus** – the mathematical description of an object or substance’s tendency to be deformed elastically (i.e., non-permanently) when a force is applied to it. The elastic modulus of an object is defined as the slope of its stress-strain curve in the elastic deformation region: As such, a stiffer material will have a higher elastic modulus.

**Elliptical** – pertaining to or having the form of an ellipse – which is a closed conic section shaped like a flattened circle, with a plane curve such that the sums of the distances of each point in its periphery from two fixed points, the foci, are equal.

**Energy neutral design** – a design of any type (Website, Multi-media, Architecture, Art, Music, Entertainment, etc.) that has the environment and low energy consumption practices in mind during all stages of planning and production.

**Epoxy** – also known as polyepoxide, epoxy is a thermosetting polymer formed from reaction of an epoxide “resin” with polyamine “hardener”. Epoxy has a wide range of applications, including fiber-reinforced plastic materials and general purpose adhesives.

**Extensive property** – a physical property of a system that is directly proportional to the system size or the amount of material in the system.

**Factor of safety** – a term describing the structural capacity of a system beyond the expected loads or actual loads.

**Fatigue** – the weakening or breakdown of material subjected to stress, especially a repeated series of stresses.

**Fish ladder** – a series of ascending pools constructed to enable salmon or other fish to swim upstream around or over a dam.

**Fluid friction** – the friction between layers within a viscous fluid that are moving relative to each other.

**Fossil fuel** – any combustible organic material, as oil, coal, or natural gas.

**French curve** – a flat drafting instrument, usually consisting of a sheet of clear plastic, the edges of which are cut into several scroll-like curves enabling a draftsperson to draw lines of varying curvature.

**French drain** – a trench covered with gravel or rock that redirects surface and groundwater away from an area (often to protect a foundation and such). A French drain can have perforated hollow pipes along the bottom to quickly vent water that seeps down through the upper gravel or rock.

**Frequency** – the number of occurrences of a repeating event per unit time, previously called cycles per second.

**Friction coefficient** – a value which describes the ratio of the force of friction between two bodies and the force pressing them together. The coefficient of friction depends on the materials used; for example, ice on steel has a low coefficient of friction, while rubber on pavement has a high coefficient of friction.

**Fulcrum** – the support, or point of rest, on which a lever turns in moving a body.

**Function** – A function is a relation between two sets in which one element of the second set is assigned to each element of the first set, as the expression *y = x ^{2}*.

**Geostationary Earth orbit** – a geosynchronous orbit directly above the Earth’s equator (0° latitude), with a period equal to the Earth’s rotational period and an orbital eccentricity of approximately zero. An object in a geostationary orbit appears motionless, at a fixed position in the sky, to ground observers.

**Girdling** – the complete removal of a strip of bark (consisting of secondary phloem tissue, cork cambium, and cork) from around the entire outer circumference of either a branch or the trunk of a woody plant. Girdling results in the death of wood tissues beyond the damage.

**Gravity of earth** – denoted *g*, refers to the acceleration that the Earth imparts to objects on or near its surface. It has an approximate value of 9.81 m/s^{2}.

**Gray** – the SI unit of absorbed radiation dose of ionizing radiation (for example, X-rays), and is defined as the absorption of one joule of ionizing radiation by one kilogram of matter (usually human tissue).

**Great ellipse** – an ellipse that passes through two points on a spheroid while having the same center as the spheroid (a spheroid is what you get when you rotate an ellipse about one of its principle axes).

**Greenhouse effect** – a process by which thermal radiation from a planetary surface is absorbed by atmospheric greenhouse gases, and is re-radiated in all directions. Since part of this re-radiation is back towards the surface and the lower atmosphere, it results in an elevation of the average surface temperature above what it would be in the absence of the gases.

**Half-life** – the period of time it takes for a substance undergoing (radioactive) decay to decrease by half.

**Hardness** – the measure of how resistant solid matter is to various kinds of permanent shape change when a force is applied.

**Hooke’s law** – an approximation that states that the extension of a spring (any material with this property) is in direct proportion with the load applied to it, ie, strain is directly proportional to stress.

**Housemaker-based model** – the Japanese custom home-purchasing model whereby the client hires what we call a housemaker — the equivalent of a large, well-funded construction firm — to build the house. Housemakers generally build model houses to showcase their designs and products.

**Immiscibility** – In chemistry, **miscibility** is the property of liquids to mix in all proportions, forming a homogeneous solution – **immiscibility** is the inability of this behavior.

**Integral** – an integral assigns numbers to functions in a way that can describe displacement, area, volume, and other concepts that arise by combining infinitesimal data. Integration is one of the two main operations of calculus, with its inverse, differentiation, being the other. See image below.

**Intensive property** – a physical property of a system that does not depend on the system size or the amount of material in the system: it is scale invariant.

**Internal friction** – the force resisting motion between the elements making up a solid material while it undergoes deformation.

**Inverse function** – a function that undoes another function: If an input x into the function f produces an output y, then putting y into the inverse function g produces the output x, and vice versa.

**Kerf** – the groove or slit created by cutting a workpiece; an incision; the width of the groove made while cutting.

**Kiln** – a thermally insulated chamber, or oven, in which a controlled temperature regime is produced. Uses include the hardening, burning or drying of materials.

**Kinetic energy** – the energy of a body or a system with respect to the motion of the body or of the particles in the system.

**Lead** – the axial travel or movement during one revolution of a screw’s rotation.

**Lithosphere** – the rigid outermost shell of a rocky planet. On Earth, it comprises the crust and the portion of the upper mantle that behaves elastically on time scales of thousands of years or greater.

**Monolith** – a geological feature such as a mountain, consisting of a single massive stone or rock, or a single piece of rock placed as, or within, a monument.

**Necking** – a mode of tensile deformation where relatively large amounts of strain localize disproportionately in a small region of the material. The resulting prominent decrease in local cross-sectional area provides the basis for the name “neck”.

**Newton** – the force required to accelerate a mass of one kilogram at a rate of one meter per second per second (1N = 1kg/m/s^{2})

**Non-enclosed angle** – in trigonometry, a non-enclosed angle is an angle where the length of one its two legs are unknown.

**Odometer** – a device that records the number of miles that a bicycle or motor vehicle has traveled.

**Ogee** – a double curve, resembling the letter S, formed by the union of a concave and a convex line.

**Opaque** – not transparent; impenetrable to light.

**Oscillation** – the repetitive variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. Familiar examples include a swinging pendulum and AC power.

**Overengineer** – Overengineering (or over-engineering) is when a product is more robust or complicated than necessary for its application, either (charitably) to ensure sufficient factor of safety, sufficient functionality, or due to design errors.

**Pascal** – The SI unit of pressure; a measure of force per unit area, defined as one newton per square meter.

**Percolation** – the slow movement of water through the pores in soil or permeable rock.

**PH** – the symbol for the logarithm of the reciprocal of hydrogen ion concentration in gram atoms per liter, used to express the acidity or alkalinity of a solution on a scale of 0 to 14, where less than 7 represents acidity, 7 neutrality, and more than 7 alkalinity.

**Placebo effect** – the phenomenon of an inert substance resulting in a patient’s medical improvement. The phenomenon is related to the perception and expectation which the patient has; if the substance is viewed as helpful, it can heal, but if it is viewed as harmful, it can cause negative effects, which is known as the nocebo effect.

**Plastic** (plastic deformation) – the deformation of a material undergoing non-reversible changes of shape due to an applied force.

**Poisson’s effect** – the ratio, when a sample object is stretched, of the contraction or transverse strain (perpendicular to the applied load), to the extension or axial strain (in the direction of the applied load).

**Ponding** – In terms of concrete curing, ponding refers to the practice of deliberately pooling water over a freshly laid concrete bed for the purpose of providing a controlled temperature and prolonged humid conditions – both of which are critical to proper curing.

**Potential energy** – the energy of a body or a system with respect to the position of the body or the arrangement of the particles of the system.

**Preload** – the load applied to a fastener merely as a result of being fastened (and before any external loads are applied).

**Pretension** – tension applied to a structural element, often prior to loading – eg, in cable to reduce sag, in concrete steel reinforcement prior to pour, released after cure to induce compression, etc.

**Radian** – the ratio between the length of an arc and its radius. Therefore, an angle of one radian results in an arc with a length equal to the radius of the circle.

**Radiation** – the process in which energy is emitted as particles or waves; the energy transferred by this process.

**Residual stress** – stresses that remain after the original cause of the stress has been removed. A typical example of residual stress is the stress exerted on a nail hammered into wood that prevents it from being removed easily.

**Resilience** – the ability of a material to absorb energy when it is deformed elastically, and release that energy upon unloading.

**Resonance chamber** – a resonance chamber uses resonance to amplify sound, having interior surfaces which reflect an acoustic wave. When a wave enters the chamber, it bounces back and forth within the chamber with low loss. As more wave energy enters the chamber, it combines with and reinforces the standing wave, increasing its intensity.

**Rip** – to saw (wood) in the direction of the grain.

**Rise over run** – the slope of a line in a plane containing x and y axes, generally represented by the letter m, and defined as the change in the y coordinate divided by the corresponding change in the x coordinate, between two distinct points on the line. In simple terms, it is the height divided by the horizontal distance spanned.

**R-value** – The R-value is a measure of thermal resistance used in the building and construction industry. Under uniform conditions it is the ratio of the temperature difference across an insulator and the heat flux (heat transfer per unit area) through it. See R-value for more information.

**Second moment of area** – a property of a cross section that can be used to predict the resistance of beams to bending and deflection, around an axis that lies in the cross-sectional plane.

**Shear modulus** – also known as modulus of rigidity; the ratio of the shear stress to the shear strain, denoted G, S, or μ, and usually expressed in gigapascals (GPa) or in thousands of pounds per square inch (kpsi). The shear modulus is always positive.

**Shear stress** – a stress which is applied parallel or tangential to a face of a material, as opposed to a normal stress which is applied perpendicularly.

**SI derived unit** – The International System of Units (SI) specifies a set of seven **base units** from which all other units of measurement are formed, by products of the powers of base units. These other units are called SI **derived units**, for example, the SI derived unit of area is square meter (m^{2}), and of density is kilograms per cubic meter (kg/m^{3}). The number of derived units is unlimited.

**Sick building syndrome** – used to describe situations in which building occupants experience acute health and comfort effects that appear to be linked to time spent in a building, but no specific illness or cause can be identified. Sick building causes are frequently pinned down to flaws in the heating, ventilation, and air conditioning (HVAC) systems. Other causes have been attributed to contaminants produced by outgassing of some types of building materials, volatile organic compounds (VOC), molds, improper exhaust ventilation of ozone (byproduct of some office machinery), light industrial chemicals used within, or lack of adequate fresh-air intake/air filtration.

**Sievert** – the SI derived unit of dose equivalent radiation. It attempts to quantitatively evaluate the biological effects of ionizing radiation as opposed to the physical aspects, which are characterised by the absorbed dose, measured in gray. Sievert has the same units of measurement as the gray, expressed as a unit of energy (joule) per unit of mass (kilogram)

**Skin friction** – a component of drag, the force resisting the motion of a solid body through a fluid.

**Spalling** – Spall are flakes of a material that are broken off a larger solid body and can be produced by a variety of mechanisms, including as a result of projectile impact, corrosion, weathering, cavitation, or excessive rolling pressure (as in a ball bearing). Spalling and spallation both describe the process of surface failure in which spall is shed.

**Specific gravity** – ratio of the density (mass of a unit volume) of a substance to the density (mass of the same unit volume) of a reference substance – usually water.

**STC** – stands for sound transmission class, STC is an integer rating of how well a building partition attenuates airborne sound. In the USA, it is widely used to rate interior partitions, ceilings/floors, doors, windows and exterior wall configurations.

**Stiffness** – the resistance of an elastic body to deformation by an applied force along a given degree of freedom (DOF) when a set of loading points and boundary conditions are prescribed on the elastic body.

**Strain-hardening** – the strengthening of a metal by plastic deformation. This strengthening occurs because of dislocation movements and dislocation generation within the crystal structure of the material.

**Stress-strain curve** – a graphical representation of the relationship between stress, derived from measuring the load applied on the sample, and strain, derived from measuring the deformation of the sample, i.e. elongation, compression, or distortion.

**Structural diaphragm** – a structural system used to transfer lateral loads to shear walls or frames primarily through in-plane shear stress. The diaphragm of a structure often does double duty as the floor system or roof system in a building, or the deck of a bridge, which simultaneously supports gravity loads.

**Submarine earthquake** – an earthquake that occurs underwater at the bottom of a body of water, especially an ocean. They are the leading cause of tsunamis.

**Thermal mass** – a concept in building design which describes how the mass of the building provides “inertia” against temperature fluctuations. Thermal mass will absorb thermal energy when the surroundings are higher in temperature than the mass, and give thermal energy back when the surroundings are cooler, without reaching thermal equilibrium. (Not to be confused with Insulation.)

**Too cheap to meter** – a concept in which a commodity is so inexpensive that it is more cost-effective and less bureaucratic to simply provide it for a flat fee or even free and make a profit from associated services.

**Torsion** – the twisting of an object due to an applied torque.

**Toughness** – the ability of a material to absorb energy and plastically deform without fracturing.

**Translucent** – a physical property that allows light to pass through, but not clearly enough to make it transparent.

**Triangle postulate** – The postulate that states that the sum of the angles of a triangle is two right angles.

**Tuck trowel** – a long, thin trowel used for pointing mortar between bricks and/or stone.

**Ultimate failure** – the complete breakage of a material or structural member.

**Viscosity** – a measure of the resistance of a fluid which is being deformed by either shear stress or tensile stress. Put simply, the less viscous the fluid is, the greater its ease of movement (fluidity).

**Yield stress or point** – the point at which a material begins to deform plastically or permanently.

**Young’s modulus** – the ratio of the uniaxial stress over the uniaxial strain in the range of stress in which Hooke’s Law holds.

- Many of the definitions contained within this Glossary are referenced from sources such as dictionary.reference.com and wikipedia.