Ab

ab
A prefix indicating that an electrical unit is part of the CGS absolute electromagnetic system.
Ab Initio
Latin meaning "from first principles".
Abacus
The uppermost part of a colurnn capital or pilaster, on which the architrave rests. Also, a bead frame used as an arithmetic calculating aid.
Abampere
The CGS electromagnetic unit of current equal to 10 Amperes.
Abamurus
A supporting wall or buttress, built to add strength to another wall.
Abaxial
Rays of light which do not coincide with the optical axis of a lens system.
Abbe Ernst
German mathematician, physicist and inventor of much optical apparatus at the Zeiss works.
Abbe Number
The ratio of refractivity to dispersion in an optical medium.
Abbe Refractometer
An instrument for measuring directly the refractive index of liquids, minerals and gemstones.
ABC Process
A method of purifying sewage which derived its name from the articles used: sulphate of alumina, blood, charcoal and clay.
Abcoulomb
The CGS unit of electric charge equal to 10 Coulomb.
ABDC
Abbreviation of After Bottom Dead Centre.
Abegg′s Rule
This states that the difference between the maximum positive and negative valence of an element is frequently eight.
Abel Flashpoint Apparatus
A petroleum-testing apparatus for determining the flash point.
Abelian Group
A mathematical group of transformations with the property that the end result of a series of transformations does not depend on the order in which they are performed.
Abend
A procedure to halt a computer program prematurely, ABnormal END.
Aberration
A defect in a mirror or lens causing light rays from a single point to fail to focus at a single point in space.
The CGS unit of capacitance equal to 1.0x109Farad.
Abhenry
The CGS unit of inductance equal to 1.0x10-9Henry.
Abhesive
A substance which prevents two materials sticking together, e.g., teflon on frying pans.
Abietic Acid

C20H30O2

A resin acid that is the primary irritant in pine wood and pine resin. It is a glassy or partly crystalline yellowish solid. It belongs to the diterpene group of organic compounds. It is used in lacquers, varnishes, and soaps, and for the analysis of resins and the preparation of metal resinates.

Abietin
Abietin is a resin obtained from Strasburg turpentine or Canada balsam. It is without taste or smell, is insoluble in water, but soluble in alcohol, in strong acetic acid, and in ether.

Abietinic Acid
Another name for Abietic Acid.
Abiogenesis
Term applied by Thomas Huxley in 1870 to the theory that living matter may be produced from non-living.
Abiotic Factor
A nonorganic variable within the ecosystem, affecting the life of organisms, e.g. temperature, light, and soil structure.
Ablate
To carry away.
Ablating Material
A material designed to provide thermal protection to a body in a fluid stream through loss of mass.
Ablating Nose Cone
A nose cone designed to reduce heat transfer to the internal structure by the use of an ablating material.
Abmho
The CGS unit that is the reciprocal of the ohm equal to 1.0x109Siemens.
Abney Level
Hand-held instrument in which angles of steep sights are measured while simultaneously viewing a spirit-level bubble.
Abney Mounting
A form of mounting for a concave diffraction grating, in which the eye-piece is fixed at the centre of curvature of the grating and the slit can move around the circumference of the Rowland circle, to bring different orders of spectrum into view.
Abohm
The CGS unit of electrical resistance equal to 1.0x10-9Ohms.
Abort
To terminate or stop a process prematurely.
We are a small consultancy formed from a group of people with very different skills in engineering, physics and software engineering.
Pertaining to a surface that has been worn by surface rubbing.
Abram′s Law
A rule that the ratio of water to cement for chemical action to impart strength to concrete is 0.85:1.
Abrasion
A process where hard particles are forced against and moved along a solid surface.
Abrasion Hardness
Resistance to abrasive wear.
Abrasion Resistance
The ability of a material to resist surface wear.
Abrasive
A very hard, brittle, heat-resistant substance that is used to grind the edges or rough surfaces of an object.
Abrasive Cleaner
A cleanser with some hard grit used to remove the grime and oils from a surface.
Abrasive Cutoff Disc
Blade-like rotating disc with abrasive particles that cuts material in a slicing motion.
Abrasive Erosion
Erosive wear caused by the relative motion of solid particles which are entrained in a fluid, moving nearly parallel to a solid surface.
Abrasive Machining
Various grinding, honing, lapping and polishing operations that utilize abrasive particles to impart new shapes, improve finishes and part stock by removing metal or other material.
Abrasive Paper
A paper upon which sand or hard grit has been glued.
Abrasive Waterjet
System that uses high-pressure waterjets in combination with a slurry of fine abrasive grains to machine materials.
Abrasive Wear
A mechanism of wear due to the presence in one or both surfaces of hard particles.
Abrasive Wheel
A grinding wheel composed of an abrasive grit and bonding agent.
ABS
Common abbreviation for Acrylonitrile Butadiene Styrene.
Abscissa
The x coordinate on an (x, y) graph.
Absolute Accuracy
A measure of the uncertainty of an instrument reading compared to that of a primary standard traceable to a National standard.
Absolute Age
The geological age of a fossil, mineral, rock or event, generally given in years.
Absolute Altitude
Altitude above the actual surface, either land or water, of a planet or natural satellite.
Absolute Brightness
The total luminosity radiated by an object.
Absolute Ceiling
The maximum altitude above sea level at which a heavier-than-air craft can be maintained in level flight.
Absolute Delay
The time interval between the transmission of sequential signals.
Absolute Error
The uncertainty in a measurement, expressed with appropriate units.
Absolute Humidity
The total mass of water vapour present in the air per unit volume, generally given in g/m3.
Absolute Instrument
An instrument whose calibration can be determined by means of physical measurements on the instrument.
Absolute Measurement
A measurement made without a direct reference to a second signal or measurement.
Absolute Motion
Motion relative to a fixed point.
Absolute Pitch
The exact pitch value of a musical note (for example, middle C)
Absolute Powder Density
The mass of powder per unit of absolute volume.
Absolute Powder Volume
The volume of the solid matter after exclusion of all the spaces ie pores and voids.
Absolute Pressure
Pressure measured from a starting point of 0 in perfect vacuum.
Absolute Space
Space that is not affected by what occupies it or occurs within it and that provides a standard for distinguishing inertial systems from other frames of reference.
Absolute System of Units
A system of units in which a small number of units are chosen as fundamental, and all other units are derived from them.
Absolute Temperature
Temperature measured on a scale that sets absolute zero as zero.
Absolute Temperature Scale
A temperature scale based upon the value zero as the lowest possible value.
Absolute Unit
A unit defined in terms of fundamental quantities.
Absolute Vacuum
A volume which contains no matter.
Absolute Value
The positive value for a real number, disregarding the sign.
Absolute Velocity
The vector sum of the velocity of a fluid parcel relative to the earth and the velocity of the parcel due to the earth′s rotation.
Absolute Vorticity
The vorticity of a fluid particle expressed with respect to an absolute coordinate system.
Absolute Zero
At this temperature atoms have no energy.
Absorb
To transform radiant energy into a different form, with a resultant rise in temperature.
Absorbed Dose
The amount of a chemical that enters the body of an exposed organism.
Absorbed Glass Mat Battery
A type of lead acid battery where the electrolyte is absorbed in a matrix of glass fibres holding the electrolyte next to the lead plates.
Absorbent
A material which, due to an affinity for certain substances, extracts one or more such substances from a liquid or gaseous medium with which it contacts.
Absorbent Ducts
There are many different sizes and applications of absorbent ducts.
Absorbent Filter
A filter medium that holds contaminant by mechanical means.
Absorbent Glass Mat Battery
A separator technology used in some sealed lead-acid batteries in which the glass-mat separator absorbs 100% of the electrolyte.
Absorbent Material
A material which absorbs energy from an incident sound wave.
Absorber
Material in a nuclear reactor that absorbs neutrons without reproducing them.
Absorption
Transformation of radiant energy to a different form of energy by the interaction of matter, depending on temperature and wavelength.
Absorption Band
A dark band in the absorption spectrum of a substance, corresponding to a range of wavelengths for which the substance absorbs more strongly than at adjacent wavelengths.
Absorption Coefficient
The fraction of sound energy that is absorbed at any surface.
Absorption Edges
Sudden rises superposed on the smooth decrease of the curve of the attenuation coefficient, which cause the curve to have a typical sawtooth aspect.
Absorption Lines
Dark lines in a spectrum that are produced when light or other electromagnetic radiation passes through a gas cloud or similar object closer to the observer.
Absorption Refrigerator
Refrigerator that creates low temperatures by using the cooling effect formed when a refrigerant is absorbed by chemical substance.
Absorption Spectroscopy
A technique for determining the concentration and structure of a substance by measuring the amount of electromagnetic radiation the sample absorbs at various wavelengths.
Absorption Spectrum
The collection of wavelengths missing from a continuous distribution of wavelengths.
Absorption Tower
A tower or column, which effects contact between a rising gas and a falling liquid, so that part of the gas may be taken up by the liquid.
Absorption Trough
Range of wavelengths at which atomic hydrogen absorbs or emits radiation.
Absorptive Index
The imaginary part of the complex index of refraction of a medium.
Absorptivity
The absorbance of a solution per unit of path length and per unit concentration.
Abstract Program
A mathematical program defined on an abstract vector space.
abtesla
The CGS unit of magnetic flux density equal to 10-4 tesla.
Abundance Ratio
The ratio of the number of atoms of an isotope to the number of atoms of another isotope of the same element in a sample.
Abundant Number
A positive integer that is smaller than the sum of its proper divisors.
Abuse Test
Testing a component or system to the extreme conditions that it will experience in real world operation.
Abut
The action of two gear teeth making contact.
Abutment
A part which stops the motion of another part from proceeding any farther.
Abutting Edge
The side or edge of a panel which joins another panel.
abv
Abbreviation of Alcohol by Volume.
Abvolt
The CGS unit of electromotive force equal to 1.0x10-9Volt.
abw
Abbreviation of Alcohol by Weight.
abwatt
The CGS unit of power equal to 10-7 watt.
abweber
The CGS unit of magnetic flux equal to 10-8 weber. Also known as the maxwell.
Abyssal Plain
Large area of extremely flat ocean floor lying near a continent and generally over 4000m deep.