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real life: A rapid and persistent chemical change that releases heat and light and is accompanied by flame, especially the exothermic oxidation of a combustible substance.contrary to popular belive in real life fire is not an element.....
so in simple terms: is a chemical reaction that makes heat and light, hense the apperance of flames
Narutoverse: one of the five basic chakra elements, its an offensive techniques that allows the user to create fire by increasing the temperature of their chakra,Fire Release is strong against wind, and of course weak against water
Fire range: Fire Release techniques are mid-to-long-ranged that cause burning and explosive damage
One fire user: Of coure ME! aka Itachi