<Table> SI base units <Tr> <Th> Unit name </Th> <Th> Unit symbol </Th> <Th> Quantity name </Th> <Th> Definition ( incomplete ) </Th> <Th> Dimension symbol </Th> </Tr> <Tr> <Th> metre </Th> <Td> m </Td> <Td> length </Td> <Td> <Ul> <Li> Original ( 1793 ) : 1 / 7007100000000000000 ♠ 10 000 000 of the meridian through Paris between the North Pole and the Equator . </Li> <Li> Interim ( 1960 ) : 7006165076373000000 ♠ 1650763. 73 wavelengths in a vacuum of the radiation corresponding to the transition between the 2p and 5d quantum levels of the krypton - 86 atom . </Li> <Li> Current ( 1983 ) : The distance travelled by light in a vacuum in 1 / 7008299792458000000 ♠ 299 792 458 second . </Li> </Ul> </Td> <Td> </Td> </Tr> <Tr> <Th> kilogram </Th> <Td> kg </Td> <Td> mass </Td> <Td> <Ul> <Li> Original ( 1793 ) : The grave was defined as being the weight ( mass ) of one cubic decimetre of pure water at its freezing point . </Li> <Li> Current ( 1889 ) : The mass of the International Prototype Kilogram ( Le Grand K ) . </Li> </Ul> </Td> <Td> </Td> </Tr> <Tr> <Th> second </Th> <Td> s </Td> <Td> time </Td> <Td> <Ul> <Li> Original ( Medieval ) : 1 / 7004864000000000000 ♠ 86 400 of a day . </Li> <Li> Interim ( 1956 ) : 1 / 7007315569259747000 ♠ 31 556 925. 9747 of the tropical year for 1900 January 0 at 12 hours ephemeris time . </Li> <Li> Current ( 1967 ) : The duration of 7009919263177000000 ♠ 9192631770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium - 133 atom . </Li> </Ul> </Td> <Td> </Td> </Tr> <Tr> <Th> ampere </Th> <Td> </Td> <Td> electric current </Td> <Td> <Ul> <Li> Original ( 1881 ) : A tenth of the electromagnetic CGS unit of current . The ( CGS ) electromagnetic unit of current is that current , flowing in an arc 1 cm long of a circle 1 cm in radius , that creates a field of one oersted at the centre . </Li> <Li> Current ( 1946 ) : The constant current which , if maintained in two straight parallel conductors of infinite length , of negligible circular cross-section , and placed 1 m apart in vacuum , would produce between these conductors a force equal to 6993200000000000000 ♠ 2 × 10 newtons per metre of length . </Li> </Ul> </Td> <Td> </Td> </Tr> <Tr> <Th> kelvin </Th> <Td> </Td> <Td> thermodynamic temperature </Td> <Td> <Ul> <Li> Original ( 1743 ) : The centigrade scale is obtained by assigning 0 ° C to the freezing point of water and 100 ° C to the boiling point of water . </Li> <Li> Interim ( 1954 ) : The triple point of water ( 0.01 ° C ) defined to be exactly 273.16 K . </Li> <Li> Current ( 1967 ) : 1 / 273.16 of the thermodynamic temperature of the triple point of water </Li> </Ul> </Td> <Td> Θ </Td> </Tr> <Tr> <Th> mole </Th> <Td> mol </Td> <Td> amount of substance </Td> <Td> <Ul> <Li> Original ( 1900 ) : The molecular weight of a substance in mass grams . </Li> <Li> Current ( 1967 ) : The amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilogram of carbon - 12 . </Li> </Ul> </Td> <Td> </Td> </Tr> <Tr> <Th> candela </Th> <Td> cd </Td> <Td> luminous intensity </Td> <Td> <Ul> <Li> Original ( 1946 ) : The value of the new candle is such that the brightness of the full radiator at the temperature of solidification of platinum is 60 new candles per square centimetre . </Li> <Li> Current ( 1979 ) : The luminous intensity , in a given direction , of a source that emits monochromatic radiation of frequency 7014540000000000000 ♠ 5.4 × 10 hertz and that has a radiant intensity in that direction of 1 / 683 watt per steradian . </Li> </Ul> </Td> <Td> J </Td> </Tr> <Tr> <Td colspan="5"> <Dl> <Dt> Note </Dt> </Dl> <Ol> <Li> Jump up ^ Interim definitions are given here only when there has been a significant difference in the definition . </Li> <Li> Jump up ^ Despite the prefix `` kilo - '' , the kilogram is the base unit of mass . The kilogram , not the gram , is used in the definitions of derived units . Nonetheless , units of mass are named as if the gram were the base unit . </Li> <Li> Jump up ^ In 1954 the unit of thermodynamic temperature was known as the `` degree Kelvin ''
<Table> SI base units <Tr> <Th> Unit name </Th> <Th> Unit symbol </Th> <Th> Quantity name </Th> <Th> Definition ( incomplete ) </Th> <Th> Dimension symbol </Th> </Tr> <Tr> <Th> metre </Th> <Td> m </Td> <Td> length </Td> <Td> <Ul> <Li> Original ( 1793 ) : 1 / 7007100000000000000 ♠ 10 000 000 of the meridian through Paris between the North Pole and the Equator . </Li> <Li> Interim ( 1960 ) : 7006165076373000000 ♠ 1650763. 73 wavelengths in a vacuum of the radiation corresponding to the transition between the 2p and 5d quantum levels of the krypton - 86 atom . </Li> <Li> Current ( 1983 ) : The distance travelled by light in a vacuum in 1 / 7008299792458000000 ♠ 299 792 458 second . </Li> </Ul> </Td> <Td> </Td> </Tr> <Tr> <Th> kilogram </Th> <Td> kg </Td> <Td> mass </Td> <Td> <Ul> <Li> Original ( 1793 ) : The grave was defined as being the weight ( mass ) of one cubic decimetre of pure water at its freezing point . </Li> <Li> Current ( 1889 ) : The mass of the International Prototype Kilogram ( Le Grand K ) . </Li> </Ul> </Td> <Td> </Td> </Tr> <Tr> <Th> second </Th> <Td> s </Td> <Td> time </Td> <Td> <Ul> <Li> Original ( Medieval ) : 1 / 7004864000000000000 ♠ 86 400 of a day . </Li> <Li> Interim ( 1956 ) : 1 / 7007315569259747000 ♠ 31 556 925. 9747 of the tropical year for 1900 January 0 at 12 hours ephemeris time . </Li> <Li> Current ( 1967 ) : The duration of 7009919263177000000 ♠ 9192631770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium - 133 atom . </Li> </Ul> </Td> <Td> </Td> </Tr> <Tr> <Th> ampere </Th> <Td> </Td> <Td> electric current </Td> <Td> <Ul> <Li> Original ( 1881 ) : A tenth of the electromagnetic CGS unit of current . The ( CGS ) electromagnetic unit of current is that current , flowing in an arc 1 cm long of a circle 1 cm in radius , that creates a field of one oersted at the centre . </Li> <Li> Current ( 1946 ) : The constant current which , if maintained in two straight parallel conductors of infinite length , of negligible circular cross-section , and placed 1 m apart in vacuum , would produce between these conductors a force equal to 6993200000000000000 ♠ 2 × 10 newtons per metre of length . </Li> </Ul> </Td> <Td> </Td> </Tr> <Tr> <Th> kelvin </Th> <Td> </Td> <Td> thermodynamic temperature </Td> <Td> <Ul> <Li> Original ( 1743 ) : The centigrade scale is obtained by assigning 0 ° C to the freezing point of water and 100 ° C to the boiling point of water . </Li> <Li> Interim ( 1954 ) : The triple point of water ( 0.01 ° C ) defined to be exactly 273.16 K . </Li> <Li> Current ( 1967 ) : 1 / 273.16 of the thermodynamic temperature of the triple point of water </Li> </Ul> </Td> <Td> Θ </Td> </Tr> <Tr> <Th> mole </Th> <Td> mol </Td> <Td> amount of substance </Td> <Td> <Ul> <Li> Original ( 1900 ) : The molecular weight of a substance in mass grams . </Li> <Li> Current ( 1967 ) : The amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilogram of carbon - 12 . </Li> </Ul> </Td> <Td> </Td> </Tr> <Tr> <Th> candela </Th> <Td> cd </Td> <Td> luminous intensity </Td> <Td> <Ul> <Li> Original ( 1946 ) : The value of the new candle is such that the brightness of the full radiator at the temperature of solidification of platinum is 60 new candles per square centimetre . </Li> <Li> Current ( 1979 ) : The luminous intensity , in a given direction , of a source that emits monochromatic radiation of frequency 7014540000000000000 ♠ 5.4 × 10 hertz and that has a radiant intensity in that direction of 1 / 683 watt per steradian . </Li> </Ul> </Td> <Td> J </Td> </Tr> <Tr> <Td colspan="5"> <Dl> <Dt> Note </Dt> </Dl> <Ol> <Li> Jump up ^ Interim definitions are given here only when there has been a significant difference in the definition . </Li> <Li> Jump up ^ Despite the prefix `` kilo - '' , the kilogram is the base unit of mass . The kilogram , not the gram , is used in the definitions of derived units . Nonetheless , units of mass are named as if the gram were the base unit . </Li> <Li> Jump up ^ In 1954 the unit of thermodynamic temperature was known as the `` degree Kelvin ''
what is the standard unit of length in the si system
what is the standard unit of length in the si system
metre
metre