Fire
From Memory Alpha, the free Star Trek reference
Fire is a form of combustion. It generally creates heat and could cause burn injuries. Some lamps used an open flame to provide light similar to candles.
The preindustrial civilization of Barkon IV incorrectly believed that fire was one of the four basic elements of the universe, along with rock, sky, and water. By exposing wood to flame, it was believed that the fire in the wood was encouraged to show itself. (TNG: "Thine Own Self")
Fire aboard a starship or space station was normally extinguished by the fire-suppression system. (DS9: "The Passenger", "The Forsaken")
Ferengi Grand Nagus Zek described getting older as "The fire dims". (DS9: "The Nagus")
The Bajoran farmer Mullibok kept an open fire place in his cottage on the Bajoran moon Jerrado. On the outside he built a kiln. After he finished working on the kiln and fired it, Major Kira fulfilled her duty and placed several fires in his cottage. Now, that his house will no longer stand, Mullibok had to leave the moon with her. (DS9: "Progress")
When the crew of Deep Space 9 experienced their imaginations becoming reality, Major Kira Nerys saw a fireball exploding in the lower pylon one. (DS9: "If Wishes Were Horses")
A fire occurred in corridor H-12-A in the habitat ring of Deep Space 9 in 2369, caused by a plasma surge. (DS9: "The Forsaken")
The same year a bomb destroyed the school on Deep Space 9's promenade. A fire damaged the rest of the school before a Bajoran could stop the fire by using a fire extinguisher. (DS9: "In the Hands of the Prophets")
The dragons of Berengaria VII breathed fire. (TOS: "This Side of Paradise")
Changelings had the ability to morph into the form of fire. (DS9: "Chimera")
