What is fire? Please explain principle of fire.

Hi, Fire is defined as a rapid chemical reaction involving heat and fuel at the presince of O2 or an oxcedising agent. For details please search for " The Fire Tetrahedron".

fire contains triangle (OXYGEN,SUITABLE TEMPRATURE,FUEL) IF ONE OF THEM IS NOT IN ACTION THEN FIRE IS NOT CREATED .

The above answers are fine but I would rather search fire in Wikipedia.

Fire is exothermic chemical reaction resulting from the combustion of fuel, heat and oxygen.  It is self-sustain process of rapid oxidation of a fuel, which produces heat and light

 

Or the proper proportionate of fuel, heat and oxygen make combustion is fire.

 

The fire tetrahedron is a better representation of the combustion process. The tetrahedron has 4 faces. The 4 faces of the fire tetrahedron are:

 

Enough oxygen to sustain combustion,

Enough heat to raise the material to its ignition temperature,

Some sort of fuel or combustible material

And the chemical, exothermic reaction

Fire is substances combine chemically with oxygen from the air and typically give out bright light, heat, and smoke. 

There is three type of principles are fuel or material, oxygen and heat (source of ignition). 

Fuel- the substance is consumed during combustion process 

Oxygen -consumed during combustion when it's chemically combined with the fuel. oxygen is present in the air at the concentration of%

Heat- it's essential to start the combustion process