Fire is the rapid oxidation of a material in the chemical process of combustion
Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame...

, releasing heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...

, light
Light or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...

, and various reaction products
Product (chemistry)
Product are formed during chemical reactions as reagents are consumed. Products have lower energy than the reagents and are produced during the reaction according to the second law of thermodynamics. The released energy comes from changes in chemical bonds between atoms in reagent molecules and...

. Slower oxidative processes like rusting or digestion
Digestion is the mechanical and chemical breakdown of food into smaller components that are more easily absorbed into a blood stream, for instance. Digestion is a form of catabolism: a breakdown of large food molecules to smaller ones....

 are not included by this definition.

The flame
A flame is the visible , gaseous part of a fire. It is caused by a highly exothermic reaction taking place in a thin zone...

is the visible portion of the fire and consists of glowing hot gases. If hot enough, the gases may become ionized to produce plasma
Plasma (physics)
In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...

. Depending on the substances alight, and any impurities outside, the color
Color or colour is the visual perceptual property corresponding in humans to the categories called red, green, blue and others. Color derives from the spectrum of light interacting in the eye with the spectral sensitivities of the light receptors...

 of the flame and the fire's intensity
Intensity (heat transfer)
In the field of heat transfer, intensity of radiation I is a measure of the distribution of radiant heat flux per unit area and solid angle, in a particular direction, defined according todq = I\, d\omega\, \cos \theta\, dAwhere...

 will be different.

Fire in its most common form can result in conflagration
A conflagration or a blaze is an uncontrolled burning that threatens human life, health, or property. A conflagration can be accidentally begun, naturally caused , or intentionally created . Arson can be accomplished for the purpose of sabotage or diversion, and also can be the consequence of...

, which has the potential to cause physical damage through burning.

Time is the substance from which I am made. Time is a river which carries me along, but I am the river; it is a tiger that devours me, but I am the tiger; it is a fire that consumes me, but I am the fire.

Jorge Luis Borges, in "A New Refutation of Time" (1946)

"Regions Caesar never knew Thy posterity shall sway; Where his eagles never flew, None invincible as they." Such the bard's prophetic words, Pregnant with celestial fire, Bending as he swept the chords Of his sweet but awful lyre.

William Cowper in "Boadicea" (1782)

It is stern work, it is perilous work, to thrust your hand in the sun And pull out a spark of immortal flame to warm the hearts of men: But Prometheus|Prometheus, torn by the claws and beaks whose task is never done, Would be tortured another eternity to go stealing fire again.

Joyce Kilmer in "The Proud Poet" in Main Street and Other Poems (1917)

Time is the school in which we learn, Time is the fire in which we burn.

Delmore Schwartz, in "Calmly We Walk Through This April's Day|Calmly We Walk Through This April's Day" in In Dreams Begin Responsibilities|In Dreams Begin Responsibilities (1938), p. 93

When you do something, you should burn yourself completely, like a good bonfire, leaving no trace of yourself.

Shunryu Suzuki, quoted in Enter the Heart of the Fire : A collection of Mystical Poems (1981) by Mary E. Giles and Kathryn Hohlwein