Metric system - wikipedia Metric system This article is about science. For history, see History of the metric system. For adoption, see Metrication. For modern metric system, see International System of Units. For a topical guide to this subject, see Outline of the metric system. For a more accessible and less technical introduction to this topic, see Introduction to the metric system. Four metric measuring devices : a tape measure in centimetres, a thermometer in degrees Celsius, a kilogram weight and a multimeter that measures volts, amperes and ohms The metric system is an internationally adopted decimal system of measurement. It is in widespread use, and where it is used, it is the only or most common system of weights and measures. It is now known as the International System of Units ( SI ). It is used to measure everyday things such as a sack of flour, the height of a person, a tank of petrol, and the speed of a car. It is also used in science, industry and trade. In its modern form, it consists of a set of electromechanical base units including metre for length, kilogram for mass, second for time and ampere as an electrical unit, and a few others, which together with their derived units, can measure any useful quantity. Metric system may also refer to other systems of related base and derived units defined before the middle of the 20th century, some of which are still in limited use today. The metric system was designed to have a set of properties that make it easy to use and widely applicable, including units based on the natural world, decimal ratios, prefixes for multiples and sub-multiples, and a structure of base and derived units. It also has a property called coherence, which means its units are related 1 : 1, so that conversion factors are unnecessary. In science, it has a property called rationalisation which eliminates certain constants of proportionality in equations of physics. The units of the metric system, originally taken from observable features of nature, are now realised by synthetic phenomena such as the microwave frequency of a caesium atomic clock which accurately measures seconds. One unit, the kilogram, remains defined by a man - made artefact. While there are numerous named derived units of the metric system, such as watt and lumen, other common quantities such as velocity and acceleration do not have their own unit, but are defined in terms of existing base and derived units such as metres per second for velocity. Though other currently or formerly widespread systems of weights and measures continue to exist, such as the British imperial system and the US customary system of weights and measures, in those systems some or all of the units are now defined in terms of the metric system, such as the US foot which is now a defined decimal fraction of a metre. The metric system is also extensible, and new base and derived units are defined as needed in fields such as radiology and chemistry. The most recent derived unit was added in 1999. Recent changes are directed toward defining base units in terms of invariant constants of physics to provide more precise realisations of units for advances in science and industry. Contents 1 Units 1.1 Base units 1.2 Derived units with special names 1.3 Auxiliary and accessory units 2 Realisation of units 3 Properties as a system 3.1 Units based on the natural world 3.2 Base and derived unit structure 3.3 Decimal ratios 3.4 Prefixes for multiples and submultiples 3.5 Coherence 3.6 Rationalisation 3.7 `` Completeness '' 4 International System of Units 4.1 Historical variants 4.1. 1 Gaussian second and the first mechanical system of units 4.1. 2 The EMU, ESU and Gaussian systems of electrical units 4.1. 3 Centimetre -- gram -- second systems 4.1. 4 International system of electrical units 4.1. 5 MKS and MKSA systems 4.1. 6 Metre -- tonne -- second systems 4.1. 7 Gravitational systems 5 Relating SI to the real world 6 Conversion table 7 See also 8 Notes 9 References 10 External links Units Base units The modern metric system consists of four electromechanical base units representing four fundamental dimensions of measure : length, mass, time and electromagnetism. The units are the metre for length, kilogram for mass, second for time, and ampere for electromagnetism. Together they are capable of measuring any known quantity. There are also three additional supplemental base units which are not independent : the kelvin, a thermodynamic measure ; the candela, a measure of irradiance ; and the mole, representing a quantity of substance. Derived units with special names There are currently 22 derived units with special names in the metric system, these are defined in terms of the base units or other named derived units. Eight of these units are electromagnetic quantities : volt, a unit of electrical potential ohm, a unit of electrical resistance tesla, a unit of magnetic flux density weber, a unit of magnetic flux farad, a unit of electrical capacitance henry, a unit of electrical inductance siemens, a unit of electrical conductance ( the inverse of ohm ) coulomb, a unit of electrical charge Four of these units are mechanical quantities : watt, a unit of mechanical or electrical power newton, a unit of mechanical force joule, a unit of mechanical, electrical or thermodynamic energy pascal, a unit of pressure Five units represent measures of electromagnetic radiation : becquerel, a unit of radioactive decay sievert, a unit of absorbed ionising radiation gray, a unit of ionising radiation lux, a unit of luminous flux lumen, a unit of luminous intensity Two units are measures of circular arcs and spherical surfaces : radian, a unit of circular arc steradian, a unit of spherical surface area Three units are miscellaneous : degree Celsius, a unit of thermodynamic temperature katal, a unit of catalytic activity ( enzymatic ) hertz, a unit of cycles per second ( inverse of second ) Auxiliary and accessory units Main article : Non-SI units mentioned in the SI Although SI, as published by the CGPM, should, in theory, meet all the requirements of commerce, science and technology, certain customary units of measure have acquired established positions within the world community. In order that such units are used consistently around the world, the CGPM catalogued such units in Tables 6 to 9 of the SI brochure. These categories are : Non-SI units accepted for use with the International System of Units ( Table 6 ). This list includes the hour and minute, the angular measures ( degree, minute and second of arc ) and the historic ( non-coherent ) metric units, the litre, tonne and hectare ( originally agreed by the CGPM in 1879 ) Non-SI units whose values in SI units must be obtained experimentally ( Table 7 ). This list includes various units of measure used in atomic and nuclear physics and in astronomy such as the dalton, the electron mass, the electron volt, the astronomical unit, the solar mass, and a number of other units of measure that are well - established, but dependent on experimentally - determined physical quantities. Other non-SI units ( Table 8 ). This list catalogues a number of units of measure that have been used internationally in certain well - defined spheres including the bar for pressure, the ångström for atomic physics, the nautical mile and the knot in navigation. Non-SI units associated with the CGS and the CGS - Gaussian system of units ( Table 9 ). This table catalogues a number of units of measure based on the CGS system and dating from the nineteenth century. They appear frequently in the literature, but their continued use is discouraged by the CGPM. The SI symbols for the metric units are intended to be identical, regardless of the language used but unit names are ordinary nouns and use the character set and follow the grammatical rules of the language concerned. For example, the SI unit symbol for kilometre is `` km '' everywhere in the world, even though the local language word for the unit name may vary. Language variants for the kilometre unit name include : chilometro ( Italian ), Kilometer ( German ), kilometer ( Dutch ), kilomètre ( French ), χιλιόμετρο ( Greek ), quilómetro / quilômetro ( Portuguese ), kilómetro ( Spanish ) and километр ( Russian ). Variations are also found with the spelling of unit names in countries using the same language, including differences in American English and British spelling. For example, meter and liter are used in the United States whereas metre and litre are used in other English - speaking countries. In addition, the official US spelling for the rarely used SI prefix for ten is deka. In American English the term metric ton is the normal usage whereas in other varieties of English tonne is common. Gram is also sometimes spelled gramme in English - speaking countries other than the United States, though this older usage is declining. In SI, which is a coherent system, the unit of power is the `` watt '', which is defined as `` one joule per second ''. In the US customary system of measurement, which is non-coherent, the unit of power is the `` horsepower '', which is defined as `` 550 foot - pounds per second '' ( the pound in this context being the pound - force ). Similarly, neither the US gallon nor the imperial gallon is one cubic foot or one cubic yard -- the US gallon is 231 cubic inches and the imperial gallon is 277.42 cubic inches. The concept of coherence was only introduced into the metric system in the third quarter of the 19th century ; in its original form the metric system was non-coherent -- in particular the litre was 0.001 m and the are ( from which the hectare derives ) was 100 m. However the units of mass and length were related to each other through the physical properties of water, the gram having been designed as being the mass of one cubic centimetre of water at its freezing point. Realisation of units The metre was originally defined to be one ten millionth of the distance between the North Pole and the Equator through Paris. Main article : Realisation ( metrology ) The base units used in the metric system must be realisable. Each of the definitions of the base units in SI is accompanied by a defined mise en pratique ( practical realisation ) that describes in detail at least one way in which the base unit can be measured. Where possible, definitions of the base units were developed so that any laboratory equipped with proper instruments would be able to realise a standard without reliance on an artefact held by another country. In practice, such realisation is done under the auspices of a mutual acceptance arrangement ( MAA ). The standard metre is defined as exactly 1 / 299,792,458 of the distance that light travels in a second. The realisation of the metre depends in turn on precise realisation of the second. There are both astronomical observation methods and laboratory measurement methods that are used to realise units of the standard metre. Because the speed of light is now exactly defined in terms of the metre, more precise measurement of the speed of light does not result in a more accurate figure for its velocity in standard units, but rather a more accurate definition of the metre. The accuracy of the measured speed of light is considered to be within 1 m / s, and the realisation of the metre is within about 3 parts in 1,000,000,000, or an order of 10 parts. The kilogram is defined by the mass of a man - made artefact of platinum - iridium held in a laboratory in France. Replicas made in 1879 at the time of the artefact 's fabrication and distributed to signatories of the Metre Convention serve as de facto standards of mass in those countries. Additional replicas have been fabricated since as additional countries have joined the convention. The replicas are subject to periodic validation by comparison to the original, called the IPK. It has become apparent that either the IPK or the replicas or both are deteriorating, and are no longer comparable : they have diverged by 50 μg since fabrication, so figuratively, the accuracy of the kilogram is no better than 5 parts in a hundred million or within an order of 10 parts. Properties as a system Although the metric system has changed and developed since its inception, its basic concepts have hardly changed. Designed for transnational use, it consisted of a basic set of units of measurement, now known as base units. Derived units were built up from the base units using logical rather than empirical relationships while multiples and submultiples of both base and derived units were decimal - based and identified by a standard set of prefixes. Units based on the natural world Like most units of measure, the units of the metric system were based on perceptual quantities of the natural world. But they also had definitions in terms of stable relationships in that world : a metre was defined not by the span of a man 's arms like a toise, but on a quantitative measure of the earth. A kilogram was defined by a volume of water, whose linear dimensions were fractions of the unit of length. The earth was n't easy to measure, nor was it uniformly shaped, but the principle that units of measure were to be based on quantitative relationships among invariant facets of the physical world was established. The units of the metric system today still adhere to that principle, but the relationships used are based on the physics of nature, rather than its sensory dimensions. Base and derived unit structure The metric system base units were originally adopted because they represented fundamental orthogonal dimensions of measurement corresponding to how we perceive nature : a spacial dimension, a time dimension, one for the effect of gravitation, and later, a more subtle one for the dimension of an `` invisible substance '' known as electricity or more generally, electromagnetism. One and only one unit in each of these dimensions was defined, unlike older systems where multiple perceptual quantities with the same dimension were prevalent, like inches, feet and yards or ounces, pounds and tons. Units for other quantities like area and volume, which are also spacial dimensional quantities, were derived from the fundamental ones by logical relationships, so that a unit of square area for example, was the unit of length squared. Many derived units were already in use before and during the time the metric system evolved, because they represented convenient abstractions of whatever base units were defined for the system, especially in the sciences. So analogous units were scaled in terms of the metric units, and their names adopted into the system. Many of these were associated with electromagnetism. Other perceptual units, like volume, which were not defined in terms of base units, were incorporated into the system with definitions in the metric base units, so that the system remained simple. It grew in number of units, but the system retained a uniform structure. Decimal ratios Some customary systems of weights and measures had duodecimal ratios, which meant quantities were conveniently divisible by 2, 3, 4, and 6. But it was n't easy to do arithmetic with things like 1 / 4 pound or 1 / 3 foot. There was no system of notation for successive fractions : for example, 1 / 3 of 1 / 3 of a foot was n't an inch or any other unit. But the system of counting in decimal ratios did have notation, and the system had the algebraic property of multiplicative closure : a fraction of a fraction, or a multiple of a fraction was a quantity in the system, like 1 / 10 of 1 / 10 which is a 1 / 100. So a decimal radix became the ratio between unit sizes of the metric system. Prefixes for multiples and submultiples Main article : metric prefix In the metric system, multiples and submultiples of units follow a decimal pattern, Metric prefixes in everyday use Text Symbol Factor Power exa 7018100000000000000 ♠ 1000000000000000000 10 peta 7015100000000000000 ♠ 1000000000000000 10 tera 7012100000000000000 ♠ 1000000000000 10 giga 7009100000000000000 ♠ 1000000000 10 mega 7006100000000000000 ♠ 1000000 10 kilo k 7003100000000000000 ♠ 1000 10 hecto h 100 10 deca da 10 10 ( none ) ( none ) 10 deci d 0.1 10 centi 0.01 10 milli m 0.001 10 micro μ 6994100000000000000 ♠ 0.000 001 10 nano n 6991100000000000000 ♠ 0.000 000 001 10 pico p 6988100000000000000 ♠ 0.000 000 000 001 10 femto f 6985100000000000000 ♠ 0.000 000 000 000 001 10 atto 6982100000000000000 ♠ 0.000 000 000 000 000 001 10 A common set of decimal - based prefixes that have the effect of multiplication or division by an integer power of ten can be applied to units that are themselves too large or too small for practical use. The concept of using consistent classical ( Latin or Greek ) names for the prefixes was first proposed in a report by the ( French Revolutionary ) Commission on Weights and Measures in May 1793. The prefix kilo, for example, is used to multiply the unit by 1000, and the prefix milli is to indicate a one - thousandth part of the unit. Thus the kilogram and kilometre are a thousand grams and metres respectively, and a milligram and millimetre are one thousandth of a gram and metre respectively. These relations can be written symbolically as : 1 mg = 0.001 g 1 km = 1000 m In the early days, multipliers that were positive powers of ten were given Greek - derived prefixes such as kilo - and mega -, and those that were negative powers of ten were given Latin - derived prefixes such as centi - and milli -. However, 1935 extensions to the prefix system did not follow this convention : the prefixes nano - and micro -, for example have Greek roots. During the 19th century the prefix myria -, derived from the Greek word μύριοι ( mýrioi ), was used as a multiplier for 7004100000000000000 ♠ 10 000. When applying prefixes to derived units of area and volume that are expressed in terms of units of length squared or cubed, the square and cube operators are applied to the unit of length including the prefix, as illustrated below. 1 mm ( square millimetre ) = ( 1 mm ) = ( 0.001 m ) = 6994100000000000000 ♠ 0.000 001 m 1 km ( square kilometre ) = ( 1 km ) = ( 1000 m ) = 7006100000000000000 ♠ 1000000 m 1 mm ( cubic millimetre ) = ( 1 mm ) = ( 0.001 m ) = 6991100000000000000 ♠ 0.000 000 001 m 1 km ( cubic kilometre ) = ( 1 km ) = ( 1000 m ) = 7009100000000000000 ♠ 1000000000 m Prefixes are not usually used to indicate multiples of a second greater than 1 ; the non-SI units of minute, hour and day are used instead. On the other hand, prefixes are used for multiples of the non-SI unit of volume, the litre ( l, L ) such as millilitres ( ml ). Coherence Main article : Coherence ( units of measurement ) James Clerk Maxwell played a major role in developing the concept of a coherent CGS system and in extending the metric system to include electrical units. Each variant of the metric system has a degree of coherence -- the various derived units are directly related to the base units without the need for intermediate conversion factors. For example, in a coherent system the units of force, energy and power are chosen so that the equations force = mass × acceleration energy = force × distance power = energy ÷ time hold without the introduction of unit conversion factors. Once a set of coherent units have been defined, other relationships in physics that use those units will automatically be true. Therefore, Einstein 's mass - energy equation, E = mc, does not require extraneous constants when expressed in coherent units. The CGS system had two units of energy, the erg that was related to mechanics and the calorie that was related to thermal energy ; so only one of them ( the erg ) could bear a coherent relationship to the base units. Coherence was a design aim of SI resulting in only one unit of energy being defined -- the joule. Rationalisation Maxwell 's equations of electromagnetism contained a factor relating to steradians, representative of the fact that electric charges and magnetic fields may be considered to emanate from a point and propagate equally in all directions, i.e. spherically. This factor appeared awkwardly in many equations of physics dealing with the dimensionality of electromagnetism and sometimes other things. `` Completeness '' The four dimensions of length, time, mass and electromagnetism underlie everything realisable, and together form the system of electromechanical units. These dimensions have an irreducible relationship to the physical world ; there must be one unit for each, or some things will not be sensibly measurable, and the system will fall into chaos or contradiction. Nothing that we know of requires another ( fifth ) orthogonal dimension and unit of measure. But because some kinds of perceptual phenomena do not have readily quantifiable dimensions in the electromechanical units, additional human - perceptual base units were defined : one for temperature, illumination, and quantity of substance. International system of units Main articles : International System of Units and List of physical quantities The International System of Units is the modern metric system. It is based on the Metre - Kilogram - Second - Ampere ( MKSA ) system of units from early in the 20th century. It also includes numerous coherent derived units for common quantities like power ( watt ) and irradience ( lumen ). Electrical units were taken from the International system then in use. Other units like those for energy ( joule ) were modeled on those from the older CGS system, but scaled to be coherent with MKSA units. Two additional base units, degree Kelvin equivalent to degree Centigrade for thermodynamic temperature, and candela, roughly equivalent to the international candle unit of illumination, were introduced. Later, another base unit, the mole, a unit of mass equivalent to Avogadro 's number of specified molecules, was added along with several other derived units. The system was promulgated by the General Conference on Weights and Measures ( French : Conférence générale des poids et mesures -- CGPM ) in 1960. At that time, the metre was redefined in terms of the wavelength of a spectral line of the krypton - 86 atom, and the standard metre artefact from 1889 was retired. Today, the International system of units consists of 7 base units and innumerable coherent derived units including 22 with special names. The last new derived unit, the katal for catalytic activity, was added in 1999. Some of the base units are now realised in terms of invariant constants of physics. As a consequence, the speed of light has now become an exactly defined constant, and defines the metre as ​ ⁄ of the distance light travels in a second. The kilogram remains defined by a man - made artefact of platinum - iridium, and it is deteriorating. The range of decimal prefixes has been extended to those for 10, yotta, and 10, yocto, which are unfamiliar because nothing in our everyday lives is that big or that small. The International System of Units has been adopted as the official system of weights and measures by all nations in the world except for Myanmar ( Burma ), Liberia, and the United States, while the United States is the only industrialised country where the metric system is not the predominant system of units. Historical variants A number of variants of the metric system evolved, all using the Mètre des Archives and Kilogramme des Archives ( or their descendants ) as their base units, but differing in the definitions of the various derived units. Variants of the metric system Quantity CGS MKS MTS distance, displacement, length, height, etc. ( d, x, l, h, etc. ) centimetre ( cm ) metre ( m ) metre mass ( m ) gram ( g ) kilogram ( kg ) tonne ( t ) time ( t ) second ( s ) second second speed, velocity ( v, v ) cm / s m / s m / s acceleration ( a ) gal ( Gal ) m / s m / s force ( F ) dyne ( dyn ) newton ( N ) sthene ( sn ) pressure ( P or p ) barye ( Ba ) pascal ( Pa ) pièze ( pz ) energy ( E, Q, W ) erg ( erg ) joule ( J ) kilojoule ( kJ ) power ( P ) erg / s watt ( W ) kilowatt ( kW ) viscosity ( μ ) poise ( P ) Pa ⋅ s pz ⋅ s Gaussian second and the first mechanical system of units In 1832, Gauss used the astronomical second as a base unit in defining the gravitation of the earth, and together with the gram and millimetre, became the first system of mechanical units. The emu, esu and Gaussian systems of electrical units Several systems of electrical units were defined following discovery of Ohm 's law in 1824. Centimetre -- gram -- second systems The centimetre -- gram -- second system of units ( CGS ) was the first coherent metric system, having been developed in the 1860s and promoted by Maxwell and Thomson. In 1874, this system was formally promoted by the British Association for the Advancement of Science ( BAAS ). The system 's characteristics are that density is expressed in g / cm, force expressed in dynes and mechanical energy in ergs. Thermal energy was defined in calories, one calorie being the energy required to raise the temperature of one gram of water from 15.5 ° C to 16.5 ° C. The meeting also recognised two sets of units for electrical and magnetic properties -- the electrostatic set of units and the electromagnetic set of units. International system of electrical units The CGS units of electricity were cumbersome to work with. This was remedied at the 1893 International Electrical Congress held in Chicago by defining the `` international '' ampere and ohm using definitions based on the metre, kilogram and second. MKS and MKSA systems In 1901, Giovanni Giorgi showed that by adding an electrical unit as a fourth base unit, the various anomalies in electromagnetic systems could be resolved. The metre -- kilogram -- second -- coulomb ( MKSC ) and metre -- kilogram -- second -- ampere ( MKSA ) systems are examples of such systems. The International System of Units ( Système international d'unités or SI ) is the current international standard metric system and is also the system most widely used around the world. It is an extension of Giorgi 's MKSA system -- its base units are the metre, kilogram, second, ampere, kelvin, candela and mole. The MKS ( Metre, Kilogram, Second ) system came into existence in 1889, when artefacts for the metre and kilogram were fabricated according to the convention of the Metre. Early in the 20th century, an unspecified electrical unit was added, and the system was called MKSX. When it became apparent that the unit would be the ampere, the system was referred to as the MKSA system, and was the direct predecessor of the SI. Metre -- tonne -- second systems The metre -- tonne -- second system of units ( MTS ) was based on the metre, tonne and second -- the unit of force was the sthène and the unit of pressure was the pièze. It was invented in France for industrial use and from 1933 to 1955 was used both in France and in the Soviet Union. Gravitational systems Gravitational metric systems use the kilogram - force ( kilopond ) as a base unit of force, with mass measured in a unit known as the hyl, Technische Mass Einheit ( TME ), mug or metric slug. Although the CGPM passed a resolution in 1901 defining the standard value of acceleration due to gravity to be 980.665 cm / s, gravitational units are not part of the International System of Units ( SI ). Relating SI to the real world The dual usage of or confusion between metric and non-metric units has resulted in a number of serious incidents. These include : Flying an overloaded American International Airways aircraft from Miami, Florida to Maiquetia, Venezuela on 26 May 1994. The degree of overloading was consistent with ground crew reading the kilogram markings on the cargo as pounds. In 1999 the Institute for Safe Medication Practices reported that confusion between grains and grams led to a patient receiving phenobarbital 0.5 grams instead of 0.5 grains ( 0.03 grams ) after the practitioner misread the prescription. The Canadian `` Gimli Glider '' accident in 1983, when a Boeing 767 jet ran out of fuel in mid-flight because of two mistakes made when calculating the fuel supply of Air Canada 's first aircraft to use metric measurements : mechanics miscalculated the amount of fuel required by the aircraft as a result of their unfamiliarity with metric units. The root cause of the loss in 1999 of NASA 's US $125 million Mars Climate Orbiter was a mismatch of units -- the spacecraft engineers calculated the thrust forces required for velocity changes using US customary units ( lbf ⋅ s ) whereas the team who built the thrusters were expecting a value in metric units ( N ⋅ s ) as per the agreed specification. Conversion Table Main article : Conversion of units During its evolution, the metric system has adopted many units of measure. The introduction of SI rationalised both the way in which units of measure were defined and also the list of units in use. These are now catalogued in the official SI Brochure. The table below lists the units of measure in this catalogue and shows the conversion factors connecting them with the equivalent units that were in use on the eve of the adoption of SI. Quantity Dimension SI unit and symbol Legacy unit and symbol Conversion factor Time second ( s ) second ( s ) Length metre ( m ) centimetre ( cm ) ångström ( Å ) 0.01 10 Mass kilogram ( kg ) gram ( g ) 0.001 Electric current ampere ( A ) international ampere abampere or biot statampere 7000100002200000000 ♠ 1.000 022 10.0 6990333564100000000 ♠ 3.335 641 × 10 Temperature Θ kelvin ( K ) degree Celsius ( ° C ) centigrade ( ° C ) ( K ) = ( ° C ) + 273.15 Luminous intensity J candela ( cd ) international candle 0.982 Amount of substance mole ( mol ) No legacy unit n / a Area square metre ( m ) are ( a ) 100 Acceleration LT ( m ⋅ s ) gal ( gal ) 10 Frequency hertz ( Hz ) cycles per second Energy L MT joule ( J ) erg ( erg ) 10 Power L MT watt ( W ) ( erg / s ) horsepower ( HP ) Pferdestärke ( PS ) 10 745.7 735.5 Force LMT newton ( N ) dyne ( dyn ) sthene ( sn ) kilopond ( kp ) 10 10 7000980665000000000 ♠ 9.806 65 Pressure L MT pascal ( Pa ) barye ( Ba ) pieze ( pz ) atmosphere ( at ) 0.1 10 7005101325000000000 ♠ 1.013 25 × 10 Electric charge IT coulomb ( C ) abcoulomb statcoulomb or franklin 10 6990333564100000000 ♠ 3.335 641 × 10 Potential difference L MT I volt ( V ) international volt abvolt statvolt 7000100034000000000 ♠ 1.000 34 10 7002299792500000000 ♠ 2.997 925 × 10 Capacitance farad ( F ) abfarad statfarad 10 6988111265000000000 ♠ 1.112 650 × 10 Inductance L MT I henry ( H ) abhenry stathenry 10 7011898755200000000 ♠ 8.987 552 × 10 Electric resistance L MT I ohm ( Ω ) international ohm abohm statohm 7000100049000000000 ♠ 1.000 49 10 7011898755200000000 ♠ 8.987 552 × 10 Electric conductance siemens ( S ) international mho ( ℧ ) abmho statmho 6999999510000000000 ♠ 0.999 51 10 6988111265000000000 ♠ 1.112 650 × 10 Magnetic flux L MT I weber ( Wb ) maxwell ( Mx ) 10 Magnetic flux density MT I tesla ( T ) gauss ( G ) 10 Magnetic field strength IL ( A / m ) oersted ( Oe ) ​ ⁄ = 7001795774700000000 ♠ 79.577 47 Dynamic viscosity ML T ( Pa ⋅ s ) poise ( P ) 0.1 Kinematic viscosity ( m ⋅ s ) stokes ( St ) 10 Luminous flux J lumen ( lm ) stilb ( sb ) 10 Illuminance JL lux ( lx ) phot ( ph ) 10 ( Radioactive ) activity becquerel ( Bq ) curie ( Ci ) 7010370000000000000 ♠ 3.70 × 10 Absorbed ( radiation ) dose gray ( Gy ) roentgen ( R ) rad ( rad ) ≈ 0.01 0.01 Radiation dose equivalent sievert roentgen equivalent man ( rem ) 0.01 Catalytic activity NT katal ( kat ) enzyme unit ( U ) 1 / 60μkat The SI Brochure also catalogues certain non-SI units that are widely used with the SI in matters of everyday life or units that are exactly defined values in terms of SI units and are used in particular circumstances to satisfy the needs of commercial, legal, or specialised scientific interests. These units include : Quantity Dimension Unit and symbol Equivalence Mass tonne ( t ) 7003100000000000000 ♠ 1000 kg Area hectare ( ha ) 0.01 km 10 m Volume litre ( L or l ) 0.001 m Time minute ( min ) hour ( h ) day ( d ) 60 s 7003360000000000000 ♠ 3600 s 7004864000000000000 ♠ 86 400 s Pressure L MT bar 100 kPa Plane angle none degree ( ° ) minute ( ′ ) second ( '' ) ( ​ ⁄ ) rad ( ​ ⁄ ) rad ( ​ ⁄ ) rad See also Binary prefix, used in computer science History of measurement ISO / IEC 80000, style manual for measurements metric and non-metric, superseding ISO 31 Metrology Units of measurement Notes Jump up ^ In German all nouns start with an upper - case letter Jump up ^ Non-SI units for time and plane angle measurement, inherited from existing systems, are an exception to the decimal - multiplier rule Jump up ^ A stable isotope of an inert gas that occurs in undetectable or trace amounts naturally Jump up ^ Roentgen is a measure of ionisation ( charge per mass ), not of absorbed dose, so there is no well - defined conversion factor. However, a radiation field of gamma rays that produces 1 roentgen of ionisation in dry air would deposit 0.0096 gray in soft tissue, and between 0.01 and 0.04 grays in bone. Since this unit was often used in radiation detectors, a factor of 0.01 can be used to convert the detector reading in roentgens to the approximate absorbed dose in grays. References Jump up ^ International Bureau of Weights and Measures ( 2006 ), The International System of Units ( SI ) ( PDF ) ( 8th ed. ), pp. 124 -- 129, ISBN 92 - 822 - 2213 - 6, archived ( PDF ) from the original on 2017 - 08 - 14 Jump up ^ International Bureau of Weights and Measures ( 2006 ), The International System of Units ( SI ) ( PDF ) ( 8th ed. ), p. 130, ISBN 92 - 822 - 2213 - 6, archived ( PDF ) from the original on 2017 - 08 - 14 Jump up ^ `` Online Translation -- Offering hundreds of dictionaries and translation in more than 800 language pairs ''. Babylon. Retrieved 5 February 2011. Jump up ^ Working Group 2 of the Joint Committee for Guides in Metrology ( JCGM / WG 2 ). ( 2008 ), International vocabulary of metrology -- Basic and general concepts and associated terms ( VIM ) ( PDF ) ( 3rd ed. ), International Bureau of Weights and Measures ( BIPM ) on behalf of the Joint Committee for Guides in Metrology, p. 9, retrieved 5 March 2011 Jump up ^ `` Weights and Measures Act 1985 ( c. 72 ) ''. The UK Statute Law Database. Office of Public Sector Information. Archived from the original on 12 September 2008. Retrieved 26 January 2011. § 92. ^ Jump up to : International Bureau of Weights and Measures ( 2006 ), The International System of Units ( SI ) ( PDF ) ( 8th ed. ), pp. 111 -- 120, ISBN 92 - 822 - 2213 - 6, archived ( PDF ) from the original on 2017 - 08 - 14 Jump up ^ `` Horsepower ''. Encyclopædia Britannica Online. 2013. Retrieved 5 April 2013. Jump up ^ MacLean, RW ( 20 December 1957 ). `` A Central Program for Weights and Measures in Canada ''. Report of the 42nd National Conference on Weights and Measures 1957. National Bureau of Standards. p. 47. Miscellaneous publication 222. Retrieved 8 May 2013. Jump up ^ JC Maxwell ( 1873 ). A treatise on electricity and magnetism. 2. Oxford : Clarendon Press. pp. 242 -- 245. Retrieved 12 May 2011. Jump up ^ `` La loi du 18 Germinal an 3 la mesure ( républicaine ) de superficie pour les terrains, égale à un carré de dix mètres de côté '' ( The law of 18 Germanial year 3 `` The republican measures of land area equal to a square with sides of ten metres '' ) ( in French ). Le CIV ( Centre d'Instruction de Vilgénis ) -- Forum des Anciens. Retrieved 2 March 2010. ^ Jump up to : Alder, Ken ( 2002 ). The Measure of all Things -- The Seven - Year - Odyssey that Transformed the World. London : Abacus. ISBN 0 - 349 - 11507 - 9. Jump up ^ `` What is a mise en pratique ? ''. BIPM. 2011. Retrieved 11 March 2011. Jump up ^ `` OIML Mutual Acceptance Arrangement ( MAA ) ''. 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( 2008 ), International vocabulary of metrology -- Basic and general concepts and associated terms ( VIM ) ( PDF ) ( 3rd ed. ), International Bureau of Weights and Measures ( BIPM ) on behalf of the Joint Committee for Guides in Metrology, 1.12, retrieved 12 April 2012 Jump up ^ Good, Michael. `` Some Derivations of E = mc '' ( PDF ). Archived from the original ( PDF ) on 7 November 2011. Retrieved 18 March 2011. Jump up ^ International Bureau of Weights and Measures ( 2006 ), The International System of Units ( SI ) ( PDF ) ( 8th ed. ), p. 109, ISBN 92 - 822 - 2213 - 6, archived ( PDF ) from the original on 2017 - 08 - 14 Jump up ^ Thomson, William ; Joule, James Prescott ; Maxwell, James Clerk ; Jenkin, Flemming ( 1873 ). `` First Report -- Cambridge 3 October 1862 ''. In Jenkin, Flemming. Reports on the Committee on Standards of Electrical Resistance -- Appointed by the British Association for the Advancement of Science. London. pp. 1 -- 3. Retrieved 12 May 2011. Jump up ^ `` Historical context of the SI -- Unit of electric current ( ampere ) ''. The NIST Reference on Constants, Units and Uncertainty. Retrieved 10 April 2011. Jump up ^ `` In the beginning... Giovanni Giorgi ''. International Electrotechnical Commission. 2011. Retrieved 5 April 2011. Jump up ^ `` System of Measurement Units ''. IEEE Global History Network. Institute of Electrical and Electronics Engineers ( IEEE ). Retrieved 21 March 2011. Jump up ^ `` Notions de physique -- Systèmes d'unités '' ( Symbols used in physics -- units of measure ) ( in French ). Hydrelect.info. Retrieved 21 March 2011. Jump up ^ Michon, Gérard P ( 9 September 2000 ). `` Final Answers ''. Numericana.com. Retrieved 11 October 2012. Jump up ^ `` Resolution of the 3rd meeting of the CGPM ( 1901 ) ''. General Conference on Weights and Measures. Retrieved 11 October 2012. Jump up ^ `` NTSB Order No. EA - 4510 '' ( PDF ). Washington, D.C. : National Transportation Safety Board. 1996. Retrieved 3 August 2008. Jump up ^ `` ISMP Medication Safety Alert ''. Institute for Safe Medication Practices. 14 July 1999. Retrieved 3 August 2008. Jump up ^ Williams, Merran ( July -- August 2003 ). `` The 156 - tonne Gimli Glider '' ( PDF ). Flight Safety Australia : 22 -- 27. Retrieved 4 December 2012. Jump up ^ `` NASA 's metric confusion caused Mars orbiter loss ''. CNN. 30 September 1999. Retrieved 21 August 2007. Jump up ^ `` Mars Climate Orbiter ; Mishap Investigation Board ; Phase I Report '' ( PDF ). NASA. 10 November 1999. Retrieved 25 August 2011. Jump up ^ `` Index to Units & Systems of Units ''. sizes.com. Archived from the original on 26 August 2012. Retrieved 9 April 2011. Jump up ^ `` Factors for Units Listed Alphabetically ''. NIST Guide to the SI. 2 July 2009. Retrieved 14 April 2011. Jump up ^ International Union of Pure and Applied Chemistry ( 1993 ). Quantities, Units and Symbols in Physical Chemistry, 2nd edition, Oxford : Blackwell Science. ISBN 0 - 632 - 03583 - 8. pp. 110 -- 116. Electronic version... Jump up ^ Fenna, Donald ( 2002 ). Oxford Dictionary of Weights, Measures and Units. Oxford : Oxford University Press. ISBN 0 - 19 - 860522 - 6. Jump up ^ BS350 : Part 1 : 1974 Conversion factors and tables Part 1. Basis of tables. Conversion factors. British Standards Institution. 1974. p. 7. 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Veloso Kevin Warwick Norbert Wiener Jennifer Wilby Anthony Wilden Applications Systems theory in anthropology Systems theory in archaeology Systems theory in political science Organizations List Principia Cybernetica Portal Commons French Revolution Causes Timeline Ancien Régime Revolution Constitutional monarchy Republic Directory Consulate Glossary Significant civil and political events by year 1788 Day of the Tiles ( 7 Jun 1788 ) Assembly of Vizille ( 21 Jul 1788 ) 1789 What Is the Third Estate ? ( Jan 1789 ) Réveillon riots ( 28 Apr 1789 ) Convocation of the Estates - General ( 5 May 1789 ) National Assembly ( 17 Jun -- 9 Jul 1790 ) Tennis Court Oath ( 20 Jun 1789 ) National Constituent Assembly ( 9 Jul -- 30 Sep 1791 ) Storming of the Bastille ( 14 Jul 1789 ) Great Fear ( 20 Jul -- 5 Aug 1789 ) Abolition of Feudalism ( 4 - 11 Aug 1789 ) Declaration of the Rights of Man and of the Citizen ( 27 Aug 1789 ) Women 's March on Versailles ( 5 Oct 1789 ) 1790 Abolition of the Parlements ( Feb -- Jul 1790 ) Abolition of the Nobility ( 19 Jun 1790 ) Civil Constitution of the Clergy ( 12 Jul 1790 ) 1791 Flight to Varennes ( 20 -- 21 Jun 1791 ) Champ de Mars Massacre ( 17 Jul 1791 ) Declaration of Pillnitz ( 27 Aug 1791 ) The Constitution of 1791 ( 3 Sep 1791 ) Legislative Assembly ( 1 Oct 1791 -- Sep 1792 ) 1792 France declares war ( 20 Apr 1792 ) Brunswick Manifesto ( 25 Jul 1792 ) Paris Commune becomes insurrectionary ( Jun 1792 ) 10th of August ( 10 Aug 1792 ) September Massacres ( Sep 1792 ) National Convention ( 20 Sep 1792 -- 26 Oct 1795 ) First republic declared ( 22 Sep 1792 ) 1793 Execution of Louis XVI ( 21 Jan 1793 ) Revolutionary Tribunal ( 9 Mar 1793 -- 31 May 1795 ) Reign of Terror ( 27 Jun 1793 -- 27 Jul 1794 ) Committee of Public Safety Committee of General Security Fall of the Girondists ( 2 Jun 1793 ) Assassination of Marat ( 13 Jul 1793 ) Levée en masse ( 23 Aug 1793 ) The Death of Marat ( painting ) Law of Suspects ( 17 Sep 1793 ) Marie Antoinette is guillotined ( 16 Oct 1793 ) Anti-clerical laws ( throughout the year ) 1794 Danton and Desmoulins guillotined ( 5 Apr 1794 ) Law of 22 Prairial ( 10 Jun 1794 ) Thermidorian Reaction ( 27 Jul 1794 ) Robespierre guillotined ( 28 Jul 1794 ) White Terror ( Fall 1794 ) Closing of the Jacobin Club ( 11 Nov 1794 ) 1795 Constitution of the Year III ( 22 Aug 1795 ) Conspiracy of the Equals ( Nov 1795 ) Directoire ( 1795 -- 99 ) Council of Five Hundred Council of Ancients 13 Vendémiaire 5 Oct 1795 1797 Coup of 18 Fructidor ( 4 Sep 1797 ) Second Congress of Rastatt ( Dec 1797 ) 1799 Coup of 30 Prairial VII ( 18 Jun 1799 ) Coup of 18 Brumaire ( 9 Nov 1799 ) Constitution of the Year VIII ( 24 Dec 1799 ) Consulate Revolutionary campaigns 1792 Verdun Thionville Valmy Royalist Revolts Chouannerie Vendée Dauphiné Lille Siege of Mainz Jemappes Namur ( fr ) 1793 First Coalition Siege of Toulon ( 18 Sep -- 18 Dec 1793 ) War in the Vendée Battle of Neerwinden ) Battle of Famars ( 23 May 1793 ) Expédition de Sardaigne ( 21 Dec 1792 - 25 May 1793 ) Battle of Kaiserslautern Siege of Mainz Battle of Wattignies Battle of Hondschoote Siege of Bellegarde Battle of Peyrestortes ( Pyrenees ) First Battle of Wissembourg ( 13 Oct 1793 ) Battle of Truillas ( Pyrenees ) Second Battle of Wissembourg ( 26 -- 27 Dec 1793 ) 1794 Battle of Villers - en - Cauchies ( 24 Apr 1794 ) Battle of Boulou ( Pyrenees ) ( 30 Apr -- 1 May 1794 ) Battle of Tournay ( 22 May 1794 ) Battle of Fleurus ( 26 Jun 1794 ) Chouannerie Battle of Tourcoing ( 18 May 1794 ) Battle of Aldenhoven ( 2 Oct 1794 ) 1795 Peace of Basel 1796 Battle of Lonato ( 3 -- 4 Aug 1796 ) Battle of Castiglione ( 5 Aug 1796 ) Battle of Theiningen Battle of Neresheim ( 11 Aug 1796 ) Battle of Amberg ( 24 Aug 1796 ) Battle of Würzburg ( 3 Sep 1796 ) Battle of Rovereto ( 4 Sep 1796 ) First Battle of Bassano ( 8 Sep 1796 ) Battle of Emmendingen ( 19 Oct 1796 ) Battle of Schliengen ( 26 Oct 1796 ) Second Battle of Bassano ( 6 Nov 1796 ) Battle of Calliano ( 6 -- 7 Nov 1796 ) Battle of the Bridge of Arcole ( 15 -- 17 Nov 1796 ) The Ireland Expedition ( Dec 1796 ) 1797 Naval Engagement off Brittany ( 13 Jan 1797 ) Battle of Rivoli ( 14 -- 15 Jan 1797 ) Battle of the Bay of Cádiz ( 25 Jan 1797 ) Treaty of Leoben ( 17 Apr 1797 ) Battle of Neuwied ( 18 Apr 1797 ) Treaty of Campo Formio ( 17 Oct 1797 ) 1798 French invasion of Switzerland ( 28 January -- 17 May 1798 ) French Invasion of Egypt ( 1798 -- 1801 ) Irish Rebellion of 1798 ( 23 May -- 23 Sep 1798 ) Quasi-War ( 1798 -- 1800 ) Peasants ' War ( 12 Oct -- 5 Dec 1798 ) 1799 Second Coalition ( 1798 -- 1802 ) Siege of Acre ( 20 Mar -- 21 May 1799 ) Battle of Ostrach ( 20 -- 21 Mar 1799 ) Battle of Stockach ( 25 Mar 1799 ) Battle of Magnano ( 5 Apr 1799 ) Battle of Cassano ( 27 Apr 1799 ) First Battle of Zurich ( 4 -- 7 Jun 1799 ) Battle of Trebbia ( 19 Jun 1799 ) Battle of Novi ( 15 Aug 1799 ) Second Battle of Zurich ( 25 -- 26 Sep 1799 ) 1800 Battle of Marengo ( 14 Jun 1800 ) Battle of Hohenlinden ( 3 Dec 1800 ) League of Armed Neutrality ( 1800 -- 02 ) 1801 Treaty of Lunéville ( 9 Feb 1801 ) Treaty of Florence ( 18 Mar 1801 ) Algeciras Campaign ( 8 Jul 1801 ) 1802 Treaty of Amiens ( 25 Mar 1802 ) Military leaders French Army Eustache Charles d'Aoust Pierre Augereau Alexandre de Beauharnais Jean - Baptiste Bernadotte Louis - Alexandre Berthier Jean - Baptiste Bessières Guillaume - Marie - Anne Brune Jean François Carteaux Jean Étienne Championnet Chapuis de Tourville Adam Philippe, Comte de Custine Louis - Nicolas Davout Louis Desaix Jacques François Dugommier Thomas - Alexandre Dumas Charles François Dumouriez Pierre Marie Barthélemy Ferino Louis - Charles de Flers Paul Grenier Emmanuel de Grouchy Jacques Maurice Hatry Lazare Hoche Jean - Baptiste Jourdan François Christophe de Kellermann Jean - Baptiste Kléber Pierre Choderlos de Laclos Jean Lannes Charles Leclerc Claude Lecourbe François Joseph Lefebvre Jacques MacDonald Jean - Antoine Marbot Jean Baptiste de Marbot François Séverin Marceau - Desgraviers Auguste de Marmont André Masséna Bon - Adrien Jeannot de Moncey Jean Victor Marie Moreau Édouard Mortier, duc de Trévise Joachim Murat Michel Ney Pierre - Jacques Osten ( fr ) Nicolas Oudinot Catherine - Dominique de Pérignon Jean - Charles Pichegru Józef Poniatowski Laurent de Gouvion Saint - Cyr Barthélemy Louis Joseph Schérer Jean - Mathieu - Philibert Sérurier Joseph Souham Jean - de-Dieu Soult Louis - Gabriel Suchet Belgrand de Vaubois Claude Victor - Perrin, Duc de Belluno French Navy Charles - Alexandre Linois Opposition Austria József Alvinczi Archduke Charles, Duke of Teschen Count of Clerfayt ( Walloon ) Karl Aloys zu Fürstenberg Friedrich Freiherr von Hotze ( Swiss ) Friedrich Adolf, Count von Kalckreuth Pál Kray ( Hungarian ) Charles Eugene, Prince of Lambesc ( French ) Maximilian Baillet de Latour ( Walloon ) Karl Mack von Leiberich Rudolf Ritter von Otto ( Saxon ) Prince Josias of Saxe - Coburg - Saalfeld Peter Vitus von Quosdanovich Prince Heinrich XV of Reuss - Plauen Johann Mészáros von Szoboszló ( Hungarian ) Karl Philipp Sebottendorf Dagobert von Wurmser Britain Sir Ralph Abercromby Admiral Sir James Saumarez Admiral Sir Edward Pellew Prince Frederick, Duke of York and Albany Dutch Republic William V, Prince of Orange Prussia Charles William Ferdinand, Duke of Brunswick - Wolfenbüttel Frederick Louis, Prince of Hohenlohe - Ingelfingen Russia Alexander Korsakov Alexander Suvorov Spain Luis Firmin de Carvajal Antonio Ricardos Other significant figures and factions Society of 1789 Jean Sylvain Bailly Gilbert du Motier, Marquis de Lafayette François Alexandre Frédéric, duc de la Rochefoucauld - Liancourt Isaac René Guy le Chapelier Honoré Gabriel Riqueti, comte de Mirabeau Emmanuel Joseph Sieyès Charles - Maurice de Talleyrand - Périgord Nicolas de Condorcet Feuillants and monarchiens Madame de Lamballe Madame du Barry Louis de Breteuil Loménie de Brienne Charles Alexandre de Calonne de Chateaubriand Jean Chouan Grace Elliott Arnaud de La Porte Jean - Sifrein Maury Jacques Necker François - Marie, marquis de Barthélemy Guillaume - Mathieu Dumas Antoine Barnave Lafayette Alexandre - Théodore - Victor, comte de Lameth Charles Malo François Lameth André Chénier Jean - François Rewbell Camille Jordan Madame de Staël Boissy d'Anglas Jean - Charles Pichegru Pierre Paul Royer - Collard Girondists Jacques Pierre Brissot Roland de La Platière Madame Roland Father Henri Grégoire Étienne Clavière Marquis de Condorcet Charlotte Corday Marie Jean Hérault Jean Baptiste Treilhard Pierre Victurnien Vergniaud Bertrand Barère de Vieuzac Jérôme Pétion de Villeneuve Jean Debry Jean - Jacques Duval d'Eprémesnil Olympe de Gouges Jean - Baptiste Robert Lindet Louis Marie de La Révellière - Lépeaux The Plain Abbé Sieyès de Cambacérès Charles François Lebrun Lazare Nicolas Marguerite Carnot Philippe Égalité Louis Philippe I Mirabeau Antoine Christophe Merlin de Thionville Jean Joseph Mounier Pierre Samuel du Pont de Nemours François de Neufchâteau Montagnards Maximilien Robespierre Georges Danton Jean - Paul Marat Camille Desmoulins Louis Antoine de Saint - Just Paul Nicolas, vicomte de Barras Louis Philippe I Louis Michel le Peletier de Saint - Fargeau Jacques - Louis David Marquis de Sade Jacques - Louis David Georges Couthon Roger Ducos Jean - Marie Collot d'Herbois Jean - Henri Voulland Philippe - Antoine Merlin de Douai Antoine Quentin Fouquier - Tinville Philippe - François - Joseph Le Bas Marc - Guillaume Alexis Vadier Jean - Pierre - André Amar Prieur de la Côte - d'Or Prieur de la Marne Gilbert Romme Jean Bon Saint - André Jean - Lambert Tallien Pierre Louis Prieur Bertrand Barère de Vieuzac Antoine Christophe Saliceti Hébertists and Enragés Jacques Hébert Jacques Nicolas Billaud - Varenne Pierre Gaspard Chaumette Charles - Philippe Ronsin Antoine - François Momoro François - Nicolas Vincent François Chabot Jean Baptiste Noël Bouchotte Jean - Baptiste - Joseph Gobel François Hanriot Jacques Roux Stanislas - Marie Maillard Charles - Philippe Ronsin Jean - François Varlet Theophile Leclerc Claire Lacombe Pauline Léon Gracchus Babeuf Sylvain Maréchal Others Charles X Louis XVI Louis XVII Louis XVIII Louis Antoine, Duke of Enghien Louis Henri, Prince of Condé Louis Joseph, Prince of Condé Marie Antoinette Napoléon Bonaparte Lucien Bonaparte Joseph Bonaparte Joseph Fesch Joséphine de Beauharnais Joachim Murat Jean Sylvain Bailly Jacques - Donatien Le Ray Guillaume - Chrétien de Malesherbes Talleyrand Thérésa Tallien Gui - Jean - Baptiste Target Catherine Théot List of people associated with the French Revolution Influential thinkers Les Lumières Beaumarchais Edmund Burke Anacharsis Cloots Charles - Augustin de Coulomb Pierre Claude François Daunou Diderot Benjamin Franklin Thomas Jefferson Antoine Lavoisier Montesquieu Thomas Paine Jean - Jacques Rousseau Abbé Sieyès Voltaire Mary Wollstonecraft Cultural impact La Marseillaise French Tricolour Liberté, égalité, fraternité Marianne Bastille Day Panthéon French Republican Calendar Cult of the Supreme Being Cult of Reason Temple of Reason Sans - culottes Metric system Phrygian cap Women in the French Revolution Symbolism in the French Revolution Historiography of the French Revolution Influence of the French Revolution NDL : 00567628 Retrieved from `` https://en.wikipedia.org/w/index.php?title=Metric_system&oldid=832982136 '' Categories : Metric system Systems of units International System of Units French inventions Hidden categories : CS1 French - 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Question: standard unit of distance in the metric system
Answer: metre