Abbreviation of Mega-Ampere = 1 million Ampere.
A volcanic crater that is produced by an explosion in an area of low relief.
Mach Number
The ratio of the speed of a body or flow of a fluid to the local speed of sound in the fluid.
Mach Wedge
The wave front semi-angle for a wake generated by supersonic motion of a body in a non-dispersive medium.
The relative ease of machining a metal.
Any mechanical or electrical device that performs a task for people.
Machine Learning
The ability of a computer to automatically gain new knowledge.
Machine Tool
A power-driven machine designed to bore, cut, drill, or grind metal or other materials.
Machinery Train
Three or more machines that must be aligned to one another.
Machinery Vibration
The vibration of rotating machinery may infer certain defects.
Machs Principle
The inertia of any particular particle or particles of matter is attributable to the interaction between that piece of matter and the rest of the Universe.
Mackerel Sky
The name given to cirrocumulus clouds with small vertical extent and composed of ice crystals.
MacPherson Strut
Suspension system which uses a lower control arm and a damper/strut which is designed to take bending loads.
Curvature of a fibre which causes loss of light.
A huge molecule made up of thousands of atoms
A pore of diameter greater than about 50 nm.
Anything big enough to be seen with the naked eye.
The technology of sound at signal amplitudes so large that linear approximations are not valid.
A time-average of many microstates; this is a state of the system that can actually be observed.
The structure of metals as revealed by examination of the etched surface of a polished specimen at a magnification not exceeding ten diameters.
Madelung Constant
A constant representing the sum of the mutual potential coulombic attractive energy of all the ions in a lattice in the equation for the energy of an ionic crystal.
Magic Square
A square array of n numbers such that sum of the n numbers in any row, column, or main diagonal is a constant.
Magic Tour
If a chess piece visits each square of a chessboard in succession, this is called a tour of the chessboard.
The melted rock produced inside the earth. When a volcano erupts, magma comes to the surface and is called lava.
Magma Chamber
An area filled with magma that lies beneath a volcano.
An alloy of magnesium and aluminium used in aircraft manufacture.

A brilliant white metal, which is relatively soft and is one of the more abundant elements in the earth’s crust.
Magnesium Aspartate


The magnesium salt of aspartic acid, is a mineral supplement.

Magnesium Benzoate


A chemical compound formed from magnesium and benzoic acid. It was once used to treat gout and arthritis.

Magnesium Bromide


Often used as a mild sedative and as an anticonvulsant for treatment of nervous disorders.

Magnesium Carbonate


White solid that occurs in nature as a mineral.

Magnesium Chloride


The principal precursor to magnesium metal, which is produced on a large scale.

Magnesium Citrate


Used medicinally as a saline laxative and to empty the bowel prior to a surgery.

Magnesium Diboride


An inexpensive and useful superconducting material.

Magnesium Dichloride
Alternative name for Magnesium Chloride.
Magnesium Diglutamate


Magnesium acid salt of glutamic acid.

Magnesium Diuranate


Forms the major part of some yellowcake mixtures that are an intermediate product in the uranium refining process.

Magnesium Fluoride
Used as antireflection coating for lenses because of its low refractive index.

Magnesium Gluconate


Magnesium salt of gluconic acid.

Magnesium Hydride


Has been studied as a potential hydrogen storage medium.

Magnesium Hydroxide


As a suspension in water, it is often called milk of magnesia because of its milk-like appearance and is used to neutralize stomach acid and as a laxative.

Magnesium Iodide


Few commercial uses but can be used to prepare compounds for organic synthesis.

Magnesium Nitrate


Hygroscopic salt that in air quickly forms the hexahydrate.

Magnesium Nitride


Reacts with water to produce ammonia gas.

Magnesium Orotate


The magnesium salt of orotic acid which is a mineral supplement.

Magnesium Oxide
Formed by igniting Magnesium in air.
Magnesium Perchlorate


Powerful oxidizing agent that is highly exothermic with addition of water.

Magnesium Peroxide


Releases oxygen by breaking down at a controlled rate with a hydrous fluid.

Magnesium Salt
Alternative name for Magnesium Stearate.
Magnesium Silicide


Used to create aluminium alloys of the 6xxx group, containing up to approximately 1.5% Mg2Si.

Magnesium Stearate


Widely regarded as harmless, it is often used as a diluent in the manufacture of medical tablets.

Magnesium Sulphate


Traditionally used as a component of bath salts.

Magnesium Sulphide


Wide band-gap direct semiconductor of interest as a blue-green emitter.

Magnesium Sulphite


Readily absorbs water from the air.

Magnesium Trisilicate


A food additive that is used as a kind of absorbent to filter unwanted residue fat from used frying oil.

A magnet is a device that produces a magnetic field.
Magnet Wire
Wire coated with an enamel insulation and used in coils, relays, transformers and motor windings.
A magnet or a material which is capable of being magnetized.
Magnetic Amplifier
An electromagnetic device that uses one or more saturable reactors to obtain a large power gain.
Magnetic Bearing
A bearing that separates comparative rotating surfaces through the use of a magnetic field.
Magnetic Confinement
Method of containing a plasma or charged particles in a finite region using magnetic fields.
Magnetic Declination
The angle between magnetic north and true north at a given point on the Earth′s surface.
Magnetic Equator
The line through those points on the earth′s surface at which magnetic dip is zero.
Magnetic Field
The region in which the magnetic forces created by a permanent magnet or by a current-carrying conductor or coil can be detected.
Magnetic Field Intensity
The force that drives the generation of rnagnetic flux in a material. it is also called magnetizing force and can be produced by the application of an electric current.
Magnetic Field Probe
A small Faraday screened loop antenna used for the detection of low impedance near field current sources.
Magnetic Field Strength
The intensity of an externally applied magnetic field.
Magnetic Flux
The surface integral of the product of the permeability of the medium and the magnetic field intensity normal to the surface.
Magnetic Flux Density
The magnetic flux density is the product of field intensity and the permeability of the medium.
Magnetic Gears
Non-contact gears that offer a number of advantages over standard gear sets.
Magnetic Hysteresis
When a ferromagnetic material is placed in an alternating magnetic field, the flux density (B) lags behind the magnetizing force (H) that causes it. The area under the hysteresis loop is the hysteresis loss per cycle, and is high for permanent magnets and low for high-permeability, low-loss magnetic materials.
Magnetic Induction
Generating a voltage in a circuit by the creation of relative motion between a magnetic field and the circuit.
Magnetic Lens
Circular electro-magnets capable of projecting a precise circular magnetic field in a specified region.
Magnetic Lines of Force
Imaginary lines used for convenience to designate the direction in which magnetic forces are acting as a result of magnetomotive force.
Magnetic Moment
This is the couple exerted on a magnet placed at right angles to a uniform field with unit magnetic flux density.
Magnetic Monopole
A hypothesized, isolated magnetic pole.
Magnetic Particle Inspection
A nondestructive method of inspection for determining the existence and extent of possible defects in ferromagnetic materials.
Magnetic Permeability
This indicates the ability of a material to support magnetic lines of flux. The magnetic permeability of a material is the product of the relative permeability of that material and the permeability of free space. The relative permeability of most nonferrous materials is near unity.
Magnetic Pole
One end of a magnet; analogous to an electric charge.
Magnetic Pressure
The pressure which a magnetic field is capable of exerting on a plasma; equal to the magnetic energy density.
Magnetic Quantum Number
Quantum number that labels different orbitals within a subshell. m can take on values from - to +.
Magnetic Saturation
The upper limit of the abilIty of a ferromagnetic material to carry flux.
Magnetic Seal
A seal that uses magnetic material, instead of springs or bellows, to provide the closing force.
Magnetic Separator
A separator that uses a magnetic field to attract and hold ferromagnetic particles.
Magnetic Susceptibility
The proportionality constant between the magnetization and the magnetic field strength.
Magnetic Trip Element
A circuit breaker trip element that uses the increasing magnetic attraction of a coil with increased current to open the circuit.
The property possessed by certain materials by which these materials can exert mechanical force on neighboring masses of magnetic materials and can cause currents to be induced in conducting bodies moving relative to the magnetized bodies.
The total magnetic moment per unit volume of material.
An electrical generator that uses permanent magnets to produce periodic pulses of alternating current.
Of or pertaining to electricity produced by or associated with magnetism.
Magnetohydrodynamic Waves
Material waves in an electrically conducting fluid in the presence of a magnetic field.
Academic discipline which studies the dynamics of electrically-conducting fluids and their interactions with magnetic fields.
An instrument used in the study of geomagnetism for measuring a magnetic element.
Magneto-Optical Recording
Erasable optical disc system using magnetic media and laser reading/writing.
The outermost environment of Earth, dominated by the Earth′s magnetic field.
The change of size and/or shape of a ferromagnetic material due to the application of a magnetic field.
Magnetron Oscillator
An electron tube that provides a high power output.
The enlargement of an object by an optical instrument.
The size of a vector quantity.
Magnesium with small amounts of aluminium and other metals—used in cladding unenriched uranium metal fuel with a non-oxidising covering to contain fission products.

The name of a wine bottle equivalent to the volume of 2 standard bottles or 1.5 litres.
Magnus Effect
A rotating cylinder in a moving fluid drags some of the fluid around with it, in its direction of rotation. This increases the speed in that region, and thus the pressure is lower generating a net force on the cylinder in that direction, perpendicular to the flow of the fluid.
Abbreviation of milliampere hour.
A very hard wood that is very durable and can be polished to a fine finish with a rich colour.
Main Bearings
The bearings that house the crankshaft within the cylinder block.
Main Diagonal
In the matrix [aij], the elements a11, a22, ..., ann.
Mains Electrical Power Specification
In the UK 230V AC 50Hz.
Mains Frequency
Electricity ac supply frequency; 50 Hz in UK, 60 Hz in US.
Mains Noise
Unwanted noise in electrical signals related to mains signals.
Major Axis
The major axis of an ellipse is it′s longest chord.
Major Planets
The four largest planets: Jupiter, Saturn, Uranus, and Neptune.
Majority Carriers
The term used in transistor design to indicate the primary current-movement process.
Malfatti Circles
Three equal circles that are mutually tangent and each tangent to two sides of a given triangle.
Malic Acid
Another name for Hydroxybutanedioic Acid.
Capable of being extended or shaped by hammering or rolling.
Malleable Cast Iron
White cast iron that has been heat treated to convert the cementite into graphite clusters; a relatively ductile cast iron.

Malpighi, Marcello
An Italian scientist and physician who studied tissues and organs microscopically and is considered the founder of microanatomy.
Malus′ Law
Malus′ law defines the transmitted intensity through 2 polarisers for a given angle between the transmission directions of said polarisers.
Software installed by stealth onto a PC for malevolent purposes.
An obsolete term for cumulonimbus mammatus, it is a portion of a cumulonimbus cloud that appears as a pouch or udder on the under surface of the cloud.
Mandelbrot Set
The most famous fractal, named after Benoit Mandelbrot. It is created by iterating an equation many times.
A precision-made tapered shaft to support work for machining between centres.
A hard, brittle, silvery coloured, metallic element which resembles iron in being moderately reactive and dissolving in cold, dilute non-oxidising acids.
Manganese Bronze
A copper alloy containing zinc, manganese and a small quantity of nickel.

Manganese Carbonate


Widely used as an additive to plant fertilizers to cure manganese deficient crops. Also used in health foods, ceramic glaze colorant and flux, and in concrete stains.

Manganese Diacetate
Alternative name for Manganese II Acetate.
Manganese II Acetate


Used as a desiccant, a catalyst, and as fertilizer.

Manganese IV Oxide


This blackish or brown solid occurs naturally as the mineral pyrolusite.

Manganese VII Oxide


Volatile liquid is highly reactive and more often discussed than observed or intentionally prepared.

Manganic Oxide
Alternative name for Manganese VII Oxide.
Alloy with 84% copper, 12% manganese and 4% nickel used in wire form for making heating elements.

An oval access door into the boiler shell, used for maintenance and cleaning.
A pipe/volume with a number of inlet and outlet pipes.
Manifold Absolute Pressure
the total pressure of air going into the engine, boost pressure plus atmospheric pressure.


Originally isolated from the secretions of the flowering ash and called manna after its resemblance to the Biblical food.

A U-shaped glass tube, partly filled with a liquid, water or mercury, employed to measure pressure.
The main bulk of the Earth, between the crust and the core, ranging from depths of about 40 to 3470 kilometers.
Mantle of a Light
The element that is heated to cause illumination such as the cloth type element in gas lights often used in yards for area lighting.
Maraging Steel
Steels which are known for possessing superior strength and toughness without losing malleability, although they cannot hold a good cutting edge.

A granular metamorphosed limestone that is often polished and used for decoration.
March Equinox
Also known as the Vernal Equinox.
Marconi Antenna
A quarter-wave antenna that is operated with one end grounded and is positioned perpendicular to the earth.
Marconi, Guglielmo
Italian inventor, known as the father of long distance radiotransmission and for his development of Marconi′s law and a radio telegraph system, which served as the foundation for the establishment of numerous affiliated companies worldwide.
Marcus, Siegfried
Austrian inventor who built and drove a carriage propelled by a two cylinder gasoline engine.
Mare Tail
The name given to thin, wispy cirrus clouds composed of ice crystals that appear as veil patches or strands, often resembling a horse′s tail.
An interval during which a signal is present.
Marking Gauge
A gauge that is used to scribe a line parallel to a reference edge or surface.
Markov, Andrei
Russian mathematician, after who Markov chains were named.
The fourth planet from the sun in our solar system.
Marsh Gas
The natural occurence of methane.
Quenching an austenitized ferrous alloy in a medium at a temperature in the upper part of the martensite range.
Martensite is a microconstituent or structure in quenched steel characterized by an acicular or needle-lie pattern on the surface of polish.
Abbreviation of Microwave Amplification by Stimulated Emission of Radiation.
A device used to deposit materials on a substrate in the desired pattern.
A property of the human auditory system by which an audio signal cannot be perceived in the presence of another audio signal.
Masking Sound
Electronically generated sound used to mask intrusive sound and enhance speech privacy.
Masking Threshold
A function in frequency and time below which an audio signal cannot be perceived by the human auditory system.
A building material such as stone, clay, brick, or concrete.
The SI unit of mass is the kilogram.
Mass Action Law
The law which describes the relation between the densities of species involved in a chemical reaction.
Mass Air Flow Sensor
A device mounted in the engines air induction system that provides an electrical signal representing the instantaneous rate of mass air flow.
Mass Charge Ratio
The ratio of the mass number of an element to the number of electronic charges gained or lost in ionization.
Mass Density
Mass per unit volume.
Mass Flow Rate
Defines the volumetric rate with which fluids flow, maintaining the equation of continuity.
Mass Law
A rule for estimating the transmission loss of a barrier in its mass controlled region.
Mass Median Particle Diameter
The particle diameter at which half the particulate mass is composed of particles larger than this diameter and half the mass is composed of particles smaller than this diameter.
Mass Number
The mass number (A) of an atom is the number of protons and neutrons it has in its nucleus.
Mass Percentage
Mass percentages express the concentration of a component in a mixture or an element in a compound.
Mass Spectrometer
An instrument for producing ions in a gas and determining their mass and hence composition.
Mass Spectrum
A plot showing the results of a mass spectrometry experiment, which shows the presence of particles with different masses as a series of sharp, separate peaks.
Mineral form of Lead II Oxide.
Mass-Velocity Ratio
A quantity mv/mr expressing the relativistic variation of mass with velocity.
A physical substance used as an input to production or manufacturing.
Material Safety Data Sheet
Safety information sheet for a particular substance that lists physical properties, hazards, cleanup and disposal procedures, fire and explosion data, and protective equipment required.
Lists all Materials topics in the Encyclopaedia
Materials Books
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Materials Calculations
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Materials Conversions
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Materials Weblinks
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Mathematical Model
A mathematical representation of a process or physical object.
Mathematical Symbols
Common symbols used in mathematics.
Lists all the Mathematics topics
Mathematics Books
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Mathematics Calculations
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Mathematics Conversions
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Mathematics Weblinks
Lists all Mathematics Weblinks in the Encyclopaedia
High-performance numeric computation language from Mathworks.
A rectangular array of elements.
Anything that has mass.
Used for digging through hard packed soil and clay.
Maudslay, Henry
Perhaps the greatest machine tool engineer of the early nineteenth century.
Maudslay, Joseph
Son of the famous inventor and engineer Henry Maudslay. Joseph worked in the family firm, Maudslay, Sons & Field and specialised in marine engineering, patenting the Oscillating engine.
The maxima are points where the value of a function is greater than other surrounding points.
In a sample of data, the largest observation.
Maximum Effective Aperture
With respect to any antenna, the ratio of the square of the incident voltage to four times the product of the incident power density and antenna radiation resistance.
Maximum Fibre Stress
Maximum tensile or compressive stress in a homogeneous flexure or torsion test specimen.
Maximum Length Sequence
A type of pseudorandom binary sequence.
Maximum Likelihood Estimate
The most accurate maximum likelihood estimate is, by definition, the mode of a data set.
Maximum Thermometer
A thermometer designed to automatically register the highest temperature attained during any time interval before it is reset.
The CGS unit of magnetic flux, equal to 1x10-8weber.
Maxwell Equations
Describe the relationship between electric and magnetic fields at any point in space as a function of charge density and electric current at such a point.
Maxwell, James Clerk
Physicist who developed the field theory of electricity and magnetism, developed electromagnetic wave theory of light and a theory on viscosity of gases based on the statistical behaviour of gas molecules.
Maxwellian Distribution
The velocity distribution, as computed in the kinetic theory of gases, of the molecules of a gas in thermal equilibrium.
Mayer, Julius Robert von
German physician and physicist. He and James Joule shared the credit for the discovery of the universal law of conservation of energy, or the first law of thermodynamics.
Mayer Method
A method of evaluating the propagation delay of a transmission line.