Abbreviation of stokes, the CGS unit of kinematic viscosity.
The ability to maintain normal characteristics.
A substance that makes a mixture more stable.
In nuclear physics if something is stable it means it does not decay.
Stable Equilibrium
A body is in stable equilibrium if it returns to its equilibrium position after it has been displaced slightly.
An instrument for determining the distance to an object of know dimension by measuring the angle subtended at the observer by the object.
Stage Support
Early energy (20 to 100ms), sound source on the stage 1m away from the microphone.
Stagger Tuning
A method of klystron tuning in which the resonant cavities are tuned to slightly different frequencies to increase the bandwidth of the amplifier.
Stagnation Enthalpy
The total energy or heat content of a system generated when the flow is brought to rest isentropically at a stagnation point.
Stagnation Pressure
Another name for Dynamic Pressure.
Stainless Steel
Any steel containing at least 10.5% Cr as the principal alloying element.
Stainless Steel 303
18% chromium, 9% nickel free machining stainless. It offers good corrosion resistance with better machinability.

Stainless Steel 304
Most versatile and widely used stainless steel. It is also known as 18/8 from the nominal composition of type 304 being 18% chromium and 8% nickel.

Stainless Steel 310
Very tough and ductile, has good resistance to oxidation in continuous service up to 1150°C used for furnace components.

Stainless Steel 316
Better overall corrosion resistance properties than 304 and higher creep strength at elevated temperatures. 316 resists chloride attack and is often selected for use in marine atmospheres.

Stainless Steel 431
Martensitic stainless steel with excellent impact strength at high hardness levels with the best corrosion resistance of any martensitic stainless steels.

A cone shaped deposit of minerals hanging from the roof of a cavern.
A post of dripstone growing up from a cave floor.
Condition which arises when the smooth airflow over a wing′s upper surface breaks down and its lift is destroyed.
Stall Torque
The maximum torque without burning out the motor.
Standard Acceleration due to Gravity
g = 9.80665 ms-2
Standard Atmosphere
Standard atmospheric pressure is equal to 101325 Pascals.
Standard Boiling Point
The temperature at which the vapour pressure of a liquid equals standard pressure.
Standard Cell
A non-rechargeable cell whose emf is accurately known and remains sufficiently constant.
Standard Cell Voltage
The reversible voltage of an electrochemical cell with all active materials in their standard states.
Standard Deviation
Standard deviation is the square root of the variance.
Standard Differential Equations
A listing of some of the standard differential equations.
Standard Electrode Potential
The reversible potential of an electrode with all the active materials in their standard states.
Standard Enthalpy Change
A change in enthalpy associated with a reaction or transformation involving substances in their standard states.
Standard Enthalpy of Formation
The change in enthalpy when one mole of compound is formed from its elements in their most stable form and in their standard states.
Standard Enthalpy of Reaction
A change in enthalpy associated with a reaction involving substances in their standard states.
Standard Entropy of Reaction
A change in entropy associated with a reaction involving substances in their standard states.
Standard Error
The standard deviation divided by the square root of the number of data values.
Standard Integrals
A listing of the standard indefinite and definite integrals.
Standard Model
Physicists' name for the theory of fundamental particles and their interactions.
Standard Molar Entropy
The entropy of one mole of a substance in its standard state.
Standard Molar Volume
The volume of 1 mole of an ideal gas at STP, equal to 22.414 litres.
Standard Normal Distribution
A normal distribution with a mean equal to 0 and a standard deviation equal to 1
Standard Rate Constant of Electrode Reaction
The rate constant of an electrode reaction at the standard electrode potential.
Standard Solution
A solution of precisely known concentration.
Standard State
A set of conditions defined to allow convenient comparison of thermodynamic properties.
Standard Temperature and Pressure
Often abbreviated as stp or STP it is a temperature of 0C and a pressure of 101325Nm-2.
Standard Wire Gauge
A numbering system for standard wire diameters, often abbreviated as SWG.
Standardized Kurtosis
A standardized form of the kurtosis statistic which renders the statistic free of scale.
Standardized Skewness
A standardized form of the skewness statistic which renders the statistic free of scale.
Standing Wave
The interference pattern produced by two waves of equal amplitude and frequency traveling in opposite directions.
Standing Wave Ratio
The ratio of the maximum to the minimum points of a wave.
Old name for Tin IV Hydride.
Stannic Fluoride
Old name for Tin IV Fluoride.
Stannic Oxide
Old name for Tin IV Oxide.
Stannous Fluoride
Old name for Tin II Fluoride.
Stannous Oxide
Old name for Tin II Oxide.
The old name for Tin and from where the chemical symbol Sn was derived.
A ball of mostly hydrogen and helium gas that shines extremely brightly. Our Sun is a star.
Star Topology
LAN topology in which each node on a network is connected directly to a central hub or concentrator.
Starburst Galaxy
Galaxy in which a large burst of star formation is observed.
A polysaccharide used by plants to stockpile glucose molecules.
Prefix to a unit in the obsolete electrostatic system of units.
The unit ofcurrent in the obsolete electrostatic system of units.
The unit of charge in the obsolete electrostatic system of units.
Solution to Schroedinger equation defined by a unique set of quantum numbers.
State of Charge
The amount of electrical charge in the battery, expressed as a percentage of the difference between the fully-charged and fully-discharged states.
State of Matter
There are three common states of matter: gases, liquids, and solids.
State Property
A state property is a quantity that is independent of how the substance was prepared.
The unit of capacitance in the obsolete electrostatic system of units.
The unit of inductance in the obsolete electrostatic system of units.
A fixed nonvarying condition, without motion.
Static Condensation (Guyan Reduction)
A Finite Element reduction technique which is used in the dynamic solution of very large problems.
Static Electricity
Stationary electricity that is in the form of a charge.
Static Equilibrium
Equilibrium which does not include inertial forces.
Static Failure
Failure when stress exceeds tensile strength in a single pass.
Static Friction
The frictional force between two surfaces at rest relative to each other.
Static Interference
Any radio interference detectable as noise in the audio stage of a receiver.
Static Limit
The distance from a rotating black hole where no observer can possibly remain at rest.
Static Pressure
A measure of the resistance of airflow through a system.
Static Random Access Memory
An integrated circuit similar to a DRAM (dynamic random access memory) with the exception that the memory does not need to be refreshed.
Static Seal
A seal between two surfaces which have no relative motion.
Static Stiffness
A measurement of the rigidity of a structure to a constant force, defined as the deflection per unit force of input.
Statically Determinate
A statically determinate structure is one where there is only one distribution of internal forces and reactions which satisfies equilibrium.
Statically Indeterminate
A statically indeterminate structure is one where there is more than one distribution of internal forces and/or reactions which satisfies equilibrium.
Stationary Phase
A substance that shows different affinities for different components in a sample mixture in a separation of the mixture by chromatography.
Stationary Seal
A mechanical seal in which the flexible members do not rotate with the shaft.
Stationary Signals
A stationary signal is a signal whose average statistical properties over a time interval of interest are constant, and it may be deterministic or not.
Anything that can be calculated from a sample of data.
Statistical Energy Analysis
A technique for analyzing the propagation through, and the sound radiation from, complex structures.
Statistical Model
A statistical model is used to describe the relationship between a dependent variable Y and one or more independent variables.
Statistical Process Control
Statistical techniques to measure and analyse the extent to which a process deviates from a set standard.
Lists all Statistics topics in the Encyclopaedia
Statistics Books
Lists all Statistics Books in the Encyclopaedia
Statistics Calculations
Lists all Statistics Calculations in the Encyclopaedia
Statistics Conversions
Lists all Statistics Conversions in the Encyclopaedia
Statistics Weblinks
Lists all Statistics Weblinks in the Encyclopaedia
The unit of conductane in the obsolete electrostatic system of units.
The unit of resistance in the obsolete electrostatic system of units.
The stationary part of a rotating electrical machine.
Statute Mile
A unit of distance most commonly used in Britain and the US.
The unit of electromotive force in the obsolete electrostatic system of units.
The unit of power in the obsolete electrostatic system of units.
Abbreviation of Sound Transmission Class, a single number rating for describing sound transmission loss of a wall or partition.
Steady State
A condition devoid of transient effects.
Steady State Sounds
Sounds whose average characteristics remain relatively constant in time.
The gas phase of water.
Steam Condenser
A device for condensing steam from the exhaust of a steam engine or turbine. Also used to condense steam that may be used in industrial processes.
Steam Drum
A cylindrical vessel mounted at a high point of a water-tube boiler.
Steam Engine
An engine that uses steam to produce useful work.
Steam Engine Indicator Diagram
The pressure in the cylinder is plotted versus the cylinder volume. This was developed by James Watt and John Southern to improve the efficiency of the steam engine. The work done is the area within the curve.
Steam Point
The temperature at which pure water can exist in equilibrium with water vapour at standard atmospheric pressure.
Steam Quality
The percentage by weight of vapour in a steam and water mixture.
Steam Reforming
The process for reacting a hydrocarbon fuel, such as natural gas, with steam to produce hydrogen as a product.
Steam Turbine
A turbine driven by steam expansion through the blades of the turbine.
An iron-based alloy containing manganese, usually carbon, and other alloying elements.
Steel EN16T
Manganese molybdenum steel with good ductile and mechanical strength and the ability to withstand shock loading.

Steel EN19T
A steel that is suitable for higher strength applications where resistance to shock is required. Typically 1% chromium molybdenum with good ductile and mechanical strength.

Steel EN1A
Low carbon free cutting mild steel. Good machining qualities.

Steel EN24T
A nickel chrome molybdenum steel with good ductile and tensile strength with good shock and wear resistance properties.

Steel EN31
A high carbon alloy steel which achieves a high degree of hardness with compressive strength and abrasion resistance.

Steel EN351
Bright / black 3/4% nickel chromium case hardening steel.

Steel EN353
Bright / black 1.1/4% nickel chromium case hardening steel.

Steel EN36
A nickel chrome case hardening steel that can be hardened to provide a very hard surface with a strong, tough core.

Steel EN42
A 0.70/0.85% carbon steel which is normally heat treated to achieve high hardness and for the production of springs.

Steel EN44
Wear-resistance makes it ideal for edge tools and scraper blades.

Steel EN45
A manganese spring steel. Untempered EN45 is harder than mild steel, and will not suffer as much from burs or require as much repair.

Steel EN47
High ratio of yield point to tensile strength and torsional fatigue strength.

Steel EN8
A medium tensile strength steel with a carbon content of 0.4 to 0.45%. The mechanical properties are just above those of mild steel. Can be heat treated to improve surface hardness.

Steel EN9
An unalloyed medium carbon steel.

The collection of components, linkages, etc. which will allow for a vessel or vehicle to follow the desired course.
Steering Angle
The angle the wheels are turned at any instance relative to straight ahead.
Steering Offset
The distance from the point where the steering axis intersects the ground to the longitudinal line that runs through the centre of the tyre′s contact patch.
Steering Ratio
The ratio of steering wheel rotation angle to steer angle at the road wheels.
Steering Shimmy
A steering wheel oscillation that often occurs at a certain road speed.
Stefan-Boltzmann Constant
σ = 5.67x10-8 Wm-2K-4
Of the stars.
Stellar Wind
A steady or unsteady outflow of material from the surface of a star.
Step Bearing
A plane surface bearing that supports the lower end of a vertical shaft.
Step by Step Counter
A counter that provides an output for each cycle of the input in one-step increments.
Step Down Transformer
A transformer so constructed that the number of turns in the secondary winding is less than the number of turns in the primary winding.
Step Engine
Another name for a multi-stage rocket.
Step Response
The response of a system to an instantaneous jump in the input signal.
Step Stressing
stresses in a series of pre-selected increments.
Step Up Transformer
A transformer so constructed that the number of turns in the secondary winding is more than the number of turns in the primary winding.
Stephenson, George
The Father of Railways, an English civil engineer and mechanical engineer who built the first public railway line in the world to use steam locomotives.
Stephenson, Robert
English civil engineer. He was the only son of George Stephenson, the famed locomotive builder and railway engineer; many of the achievements popularly credited to his father were actually the joint efforts of father and son.
Stepper Motors
Stepper motors are a special case of Brushless DC Motors.
The steradian is the solid angle, having its vertex in the centre of a sphere, cuts off an area of the surface of the sphere equal to that of a square with sides of equal length to the radius of the sphere.
1 stere = 1 m3
From the Greek meaning solid.
Stereo Irrelevance
A portion of a stereo audio signal which does not contribute to spatial perception.
The study of how the properties of a compound are affected by the spatial positions of groups within its molecules.
These are molecules with the same structural formula but their atoms have different positions in space.
Pertaining to the use of binocular vision.
A class of lipids containing the steroid nucleus.
The unit of force in the metre-tonne-second system.
A single number that indicates the effect of a transmission system on speech intelligibility.
Old name for Antimony Hydride.
The old name for Antimony and from where the chemical symbol Sb was derived.
The main source of antimony, a widely distributed but not very plentiful ore.
Stickoff Voltage
A low voltage used in multispeed synchrosystems to prevent false synchronizations.
Stiction can be defined as a form of friction which is resistance to the start of movement.
Stiffened Suspension Bridge
A suspension bridge with a stiff horizontal deck.
Stiffness is the ratio of change of force (or torque) to the corresponding change in translation (or rotational) deflection of an elastic element.
Stilling Well
A cylinder installed near a body of water is used to hold and protect hydrological sensors.
Stimulated Emission
The emission of a photon from an atom due to the presence of an incident photon.
Stirling Engine
An external combustion engine.
Stochastic Process
That which maintains a statistically random distribution.
Stoichiometric Combustion
Just sufficient air is present for complete combustion of the fuel.
The study of the relationships between amounts of products and reactants.
The CGS unit of kinematic viscosity. Abbreviated as St. 1St=1x10-4m2s-1.
Traditionally used to express the weight of a person.
Stone Masons Level
A wooden frame from which is suspended a plumb bob to find a horizontal level.
Stopping Distance
The minimum distance for a given speed that a vehicle takes to come to a rest, normally includes driver reaction time and braking distance.
Stopping Point
Hemmugspunkt: the end of the highly luminous path of a visual meteor.
The generic term for any method of storing information which is not lost when the computer is switched off.
Storage Life
The amount of time a material can be stored and remain suitable for use.
Storage Ring
A circular structure in which either high energy electrons and/or positrons, or protons and/or antiprotons are circulated many times before being used in collisions.
Stored Mechanical Energy
Energy stored in objects through the application of force eg springs.
Storm Glasses
Name given to a water based barometer.
Floor of a skyscraper.
An abbreviation of standard temperature and pressure. It is a temperature of 0C and a pressure of 101325Nm-2.
Straight Angle
An angle whose measure is 180 degrees.
Straight Engine
All of the cylinders are aligned and on one side of an aligned crank.
Straight Line
A straight set of points that continue on to infinity in both directions.
Straight Oil
A mineral oil containing no additives.
Straight-Cut Gear
A gear with teeth cut around the perimeter that are inline with the shaft on which it rotates.
As it sounds, an unmarked tool used to draw straight lines.
Straight-Line Speed
The highest speed obtainable by a vehicle driving in a straight line.
Straight-Through Silencer
A type of absorption silencer with a single perforated tube surrounded by sound-absorbing fibre. This results in a very low back pressure silencer, but at the same time only attenuates higher frequency noise.
Defined as the change in length divided by the original length of the element.
Strain Energy
Elastic energy stored in a body which has been deformed by internal or external force.
Strain Gauge
A sensor that experiences a change in resistance when it is stretched or strained.
Strain Gauge Pressure Transducer
A device measuring changes in electrical resistance in response to pressure changes on a diaphragm with an embedded or engraved strain gauge.
Strain Hardening
An increase in hardness and strength caused by plastic deformation at temperatures lower than the recrystallization range.
Strain Hardening Exponent
Measure of increase in hardness and strength caused by plastic deformation. It is related to true stress and true strain.
Strain Point
Temperature at which internal stress in glass is substantially relieved in about 1 hour.
Strain Rate
Time rate of elongation.
A coarse filter element.
Strain-Life Analysis
Models plasticity and low cycle fatigue.
Stranded Conductor
A conductor composed of a group of wires.
The flavor of the third quark.
Strange Particle
A particle with a nonzero value of strangeness.
Strange Quark
The third flavour of quark, in order of increasing mass, with electric charge -1/3.
Strap Hinge
A surface hinge of which both leaves are of considerable length.
Stratified Fluid
In a stratified fluid the density varies with depth.
Clouds composed of water droplets that exhibit no or have very little vertical development.
A low cloud composed of layers or patches of cloud elements.
Located between the troposphere and the ionosphere.
A steep volcanic cone built by both lava flows and airborne rocks and ash.
Stratum Clock
A clock in a telecommunications system or network that is assigned a number that indicates its quality and position in the timing hierarchy.
One of the three basic cloud forms.
Stratus Fractus
Stratus clouds that appear in irregular fragments.
Stray Current Corrosion
A form of attack caused by electrical currents going through an unintentional path.
Having a smooth even shape that offers the least resistance to movement through the air.
This relates to the maximum force which can be applied to a material without it breaking.
Strength Reduction Ratio
Alternate term for fatigue notch factor.
Defined as the force per unit area of cross-section.
Stress Amplitude
One-half the range of fluctuating stress developed in a specimen in a fatigue test.
Stress Concentration
A condition in which a stress distribution has high localized stresses; usually induced by an abrupt change in the shape of the part (eg holes, corners, necks).
Stress Concentration Factor
Ratio of the greatest stress in the area of a notch or other stress raiser to the corresponding nominal stress.
Stress Corrosion
Preferential attack of areas under stress in a corrosive environment, where such an environment alone would not have caused corrosion.
Stress Corrosion Cracking
Material deterioration due to cracking, by being under static stress either applied or residual.
Stress Intensity Factor
A scale factor to define the magnitude of the crack-tip stress field.
Stress Raisers
Changes in contour or discontinuities in a structure that cause local increases in stress.
Stress Ratio
Ratio of minimum stress to maximum stress in one cycle of loading in a fatigue test.
Stress Relaxation
Rate of reduction of stress in a material due to creep.
Stress Relieving
Heating to a suitable temperature, holding long enough to reduce residual stresses and then cooling slowly enough to minimize the development of new residual stresses.
Stress Resultant
A system of forces which is statically equivalent to a stress distribution over an area.
Stress Rupture Strength
Alternative name for Creep Rupture Strength.
Stressed Member
A component that is an integral part of the whole structure.
Stress-Life Analysis
Analysis technique works best for high cycle fatigue.
Stress-Rupture Test
A tension test performed at constant temperature, the load being held at such a level as to cause rupture.
Stress-Strain Diagram
Graph of stress as a function of strain.
Stress-Strain Ratio
Stress divided by strain at any load or deflection, below the elastic limit of a material it is equal to tangent modulus of elasticity.
Stretcher Bond
A particular arrangement of bricks.
Stribeck Curve
This relates friction between load-bearing surfaces as a function of relative oil film thickness and lubrication regime.
String Line
Line usually out of string, used as an aid to creating straight lines.
String Theory
A theory of elementary particles incorporating relativity and quantum mechanics in which the particles are viewed not as points but as extended objects.
Horizontal timber supporting other members of the frame in a wood or brick structure.
Stringer Inclusion
An impurity, metallic or non-metallic, which is trapped in the ingot and elongated subsequently in the direction of working.
A technique for removing volatile components in a mixture by bubbling a stream of an chemically unreactive gas through the sample, and then scrubbing the nitrogen through a solution or solid adsorbent that can recover the volatile materials.
Stripping Analysis
A group of electroanalytical techniques for the determination of trace amounts of substances.
An instrument that allows viewing of rotating or reciprocating objects by producing the optical effect of a slowing down or stopping motion.
The distance a piston travels up or down inside the cylinder.
The space and aqueous solution enclosed within the inner membrane of a chloroplast.
Strombolian Eruption
A type of volcanic eruption characterized by jetting of clots or fountains of fluid basaltic lava from a central crater.
Strong Acid
An acid that completely dissociates into hydrogen ions and anions in solution.
Strong Anthropic Principle
Implies that if the laws of the Universe were not conducive to the development of intelligent creatures to ask about the initial conditions of the Universe.
Strong Base
A base that completely dissociates into ions in solution.
Strong Electrolyte
A strong electrolyte is a solute that completely dissociates into ions in solution.
Strong Force
The force responsible for holding the nucleons together to form nuclei.
Strong Interaction
The interaction responsible for binding quarks and gluons to make hadrons.
Strong Ligand
A ligand that causes a large crystal field splitting which results in a low-spin complex.
Forms a protective stable oxide coating but it will burn in air and reacts with water.
Strouhal Number
A dimensionless unit.
Structural Acoustic Coupling
The physics relating to the vibration of a panel and the sound radiated from it or the acoustic excitation excitation of the panel.
Structural Adhesive
An adhesive used for transferring loads between adherends.
Structural Bond
A bond joining load-bearing components of an assembly.
Structural Engineer
An engineer who investigates the behaviour and design of all kinds of structures.
Structural Formula
A formula which shows the arrangement of the atoms in a molecule.
Structural Isomerism
These are molecules with the same molecular formula but with different structural arrangements of atoms.
Structural Model
An idealization for analysis purposes of a real or conceived structure.
Structural Modification
Mathematically determining the effect of changing the mass, stiffness, or damping of a structure and determining its new modal parameters.
Structure-Borne Sound
Sound for which a significant portion of the transmission path from source to receiver takes place in a solid structure rather than through a liquid or gas.
Structured Audio
MPEG-4 is a structured audio format that describes sounds and transmits the description.
Structured Query Language
A syntax used by many database systems to retrieve and modify information.
Slender structural element that resists compressive forces acting lengthwise.
A fastener which is threaded at both ends with an unthreaded shank in between.
Stud Finder
A small electrical tool that can accurately find the position of studs in a framed wall.
Student′s t Distribution
A probability distribution which is very similar in shape to the standard normal distribution.
Stuffing Box
The annular chamber provided around a valve stem in a sealing system into which deformable packing is introduced.


Colourless oily liquid that evapourates easily and has a sweet smell, it is the precursor to polystyrene and several copolymers.

Styrene Acrylonitrile
A copolymer plastic consisting of styrene and acrylonitrile widely used in place of polystyrene owing to its greater thermal resistance.

Styrene Butadiene
A synthetic rubber copolymer consisting of styrene and butadiene. Good abrasion resistance and ageing stability when protected by additives and as such is widely used in car tyres where it is blended with natural rubber.