Fundamental vs Derived Quantities
Experimentation is a core aspect of physics and other physical sciences. Theories and other hypothesis are verified and established as scientific truth by means of experiments conducted. Measurements are an integral part of experiments, where the magnitudes of and the relations amongst different physical quantities are used to verify the truth of the theory or hypothesis tested.
There are very common set of physical quantities that are often measured in physics. These quantities are considered as fundamental quantities by convention. Using the measurements for these quantities and the relations amongst them, other physical quantities can be derived. These quantities are known as derived physical quantities.
Fundamental Quantities
A set of fundamental units are defined in every units system, and the corresponding physical quantities are called the fundamental quantities. Fundamental units are independently defined, and often the quantities are directly measurable in a physical system.
In general, a system of units requires three mechanical units (mass, length, and time). One electrical unit is also required. Even though above set of units may suffice, for convenience few other physical units are considered fundamental. c.g.s (centimetergramsecond), m.k.s (meterkilogram second), and f.p.s (feetpoundsecond) are formerly used systems with fundamental units.
SI unit system has replaced much of the older units systems. In the SI system of units, by definition, following seven physical quantities are considered as fundamental physical quantities and their units as fundamental physical units.
Quantity  Unit  Symbol  Dimensions 
Length  Meter  m  L 
Mass  Kilogram  kg  M 
Time  Seconds  s  T 
Electric Current  Ampère  A 

Thermodynamic Temp.  Kelvin  K 

Amount of Substance  Mole  mol 

Luminous intensity  Candela  cd 

Derived Quantities
Derived quantities are formed by product of powers of fundamental units. In other words, these quantities can be derived using fundamental units. These units are not defined independently; they depend on the definition of other units. Quantities attached to derived units are called derived quantities.
For example, consider the vector quantity of speed. By measuring the distance traveled by an object and the time taken, the average speed of the object can be determined. Therefore, speed is a derived quantity. Electric charge is also a derived quantity where it is given by the product of current flow and time taken. Each derived quantity has derived units. Derived quantities can be formed.
Physical Quantity  Unit  Symbol  
plane angle  Radian ^{(a)}  rad    m·m^{1 }= 1 ^{(b)} 
solid angle  Steradian ^{(a)}  sr ^{(c)}    m^{2}·m^{2 }= 1 ^{(b)} 
frequency  Hertz  Hz    s^{1} 
force  Newton  N    m·kg·s^{2} 
pressure, stress  Pascal  Pa  N/m^{2}  m^{1}·kg·s^{2} 
energy, work, quantity of heat  Joule  J  N·m  m^{2}·kg·s^{2} 
power, radiant flux  Watt  W  J/s  m^{2}·kg·s^{3} 
electric charge, quantity of electricity  Coulomb  C    A·s 
electric potential difference,  Volt  V  W/A  m^{2}·kg·s^{3}·A^{1} 
capacitance  Farad  F  C/V  m^{2}·kg^{1}·s^{4}·A^{2} 
electric resistance  Ohm  V/A  m^{2}·kg·s^{3}·A^{2}  
electric conductance  Siemens  S  A/V  m^{2}·kg^{1}·s^{3}·A^{2} 
magnetic flux  Weber  Wb  V·s  m^{2}·kg·s^{2}·A^{1} 
magnetic flux density  Tesla  T  Wb/m^{2}  kg·s^{2}·A^{1} 
inductance  Henry  H  Wb/A  m^{2}·kg·s^{2}·A^{2} 
Celsius temperature  Degree Celsius  °C    K 
luminous flux  Lumen  lm  cd·sr ^{(c)}  m^{2}·m^{2}·cd = cd 
illuminance  Lux  lx  lm/m^{2}  m^{2}·m^{4}·cd = m^{2}·cd 
activity (of a radionuclide)  Becquerel  Bq    s^{1} 
absorbed dose, specific energy (imparted), kerma  Gray  Gy  J/kg  m^{2}·s^{2} 
dose equivalent ^{(d)}  Sievert  Sv  J/kg  m^{2}·s^{2} 
catalytic activity  Katal  kat  s^{1}·mol 
What is the difference between Fundamental and Derived Quantities?
• Fundamental quantities are the base quantities of a unit system, and they are defined independent of the other quantities.
• Derived quantities are based on fundamental quantities, and they can be given in terms of fundamental quantities.
• In SI units, derived units are often given names of people such as Newton and Joule.