Definitions of SI Base Units in 11th class chemistry

Unit of length	metre	The metre is the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second.
Unit of mass	kilogram	The kilogram is the unit of mass; it is equal to the mass of the international prototype of the kilogram.
Unit of time	second	The second is the duration of 1 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium - 133 atom.
Unit of electric current	ampere	The ampere is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 metre apart in vacuum, would produce between these conductors a force equal to 2 ✖ 10⁻⁷ newton per metre of length.
Unit of  thermodynamic temperature	kelvin	The kelvin, unit of thermodynamic temperature, is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water.
Unit of amount of substance	mole	1. The mole is the amount of  substance of a system which contains as many elementary entities as there are atoms in 0.012 kilogram of carbon-12; its symbol is "mol." 2. When the mole is used, the elementary entities  must be specified and may be atoms, molecules, ions, electrons, other particles, or specified of such particles.
Unit of  luminous intensity	candela	The candela is the luminous intnsity, in a given direction, of a source that emits monochromatic radiation of frequency 540 ✖ 10¹² hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.