International System of Units

In 1960, an International committee agreed on a set of definitions and standard to describe the Physical Quantities.This System that was established is called the System International (SI).
There are to types of SI Unites which are give below by there name and symbols.
 SI BASE UNITS 
                              

Table 1.  SI base units

SI base unit Base quantity Name Symbol length meter m mass kilogram       kg time second s electric current ampere A thermodynamic temperature       kelvin K amount of substance mole mol luminous intensity candela cd

SI DERIVED UNITS

            

Table 2.  Examples of SI derived units
	SI derived unit
Derived quantity	Name	Symbol
area	square meter	m2
volume	cubic meter	m3
speed, velocity	meter per second	m/s
acceleration	meter per second squared	m/s2
wave number	reciprocal meter	m-1
mass density	kilogram per cubic meter	kg/m3
specific volume	cubic meter per kilogram	m3/kg
current density	ampere per square meter	A/m2
magnetic field strength	ampere per meter	A/m
amount-of-substance concentration	mole per cubic meter	mol/m3
luminance	candela per square meter	cd/m2
mass fraction	kilogram per kilogram, which may be represented by the number 1	kg/kg = 1

Table 3.  SI derived units with special names and symbols SI derived unit Derived quantity Name Symbol   Expression in terms of other SI units Expression in terms of SI base units plane angle radian (a) rad   - m·m-1 = 1 (b) solid angle steradian (a) sr (c)   - m2·m-2 = 1 (b) frequency hertz Hz   - s-1 force newton N   - m·kg·s-2 pressure, stress pascal Pa N/m2 m-1·kg·s-2 energy, work, quantity of heat   joule J N·m m2·kg·s-2 power, radiant flux watt W J/s m2·kg·s-3 electric charge, quantity of electricity coulomb C   - s·A electric potential difference, electromotive force volt V W/A m2·kg·s-3·A-1 capacitance farad F C/V m-2·kg-1·s4·A2 electric resistance ohm V/A m2·kg·s-3·A-2 electric conductance siemens S A/V m-2·kg-1·s3·A2 magnetic flux weber Wb V·s m2·kg·s-2·A-1 magnetic flux density tesla T Wb/m2 kg·s-2·A-1 inductance henry H Wb/A m2·kg·s-2·A-2 Celsius temperature degree Celsius °C   - K luminous flux lumen lm cd·sr (c) m2·m-2·cd = cd illuminance lux lx lm/m2 m2·m-4·cd = m-2·cd activity (of a radionuclide) becquerel Bq   - s-1 absorbed dose, specific energy (imparted), kerma gray Gy J/kg m2·s-2 dose equivalent (d) sievert Sv J/kg m2·s-2 catalytic activity katal kat s-1·mol
Table 4.  Examples of SI derived units whose names and symbols include SI derived units with special names and symbols SI derived unit Derived quantity Name Symbol dynamic viscosity pascal second Pa·s moment of force newton meter N·m surface tension newton per meter N/m angular velocity radian per second rad/s angular acceleration radian per second squared rad/s2 heat flux density, irradiance watt per square meter W/m2 heat capacity, entropy joule per kelvin J/K specific heat capacity, specific entropy joule per kilogram kelvin J/(kg·K) specific energy joule per kilogram J/kg thermal conductivity watt per meter kelvin W/(m·K) energy density joule per cubic meter J/m3 electric field strength volt per meter V/m electric charge density coulomb per cubic meter C/m3 electric flux density coulomb per square meter C/m2 permittivity farad per meter F/m permeability henry per meter H/m molar energy joule per mole J/mol molar entropy, molar heat capacity joule per mole kelvin J/(mol·K) exposure (x and  rays) coulomb per kilogram C/kg absorbed dose rate gray per second Gy/s radiant intensity watt per steradian W/sr radiance watt per square meter steradian W/(m2·sr) catalytic (activity) concentration katal per cubic meter kat/m3