1550s, from Middle French cube (13c.) and directly from Latin cubus, from Greek kybos a cube, a six-sided die, vertebra, perhaps from PIE root *keu(b)- to bend, turn..
The triangle illustrates the three elements a fire needs to ignite: heat, fuel, and an oxidizing agent (usually oxygen). A fire naturally occurs when the elements are present and combined in the right mixture, meaning that fire is actually an event rather than a thing. A fire can be prevented or extinguished by removing any one of the elements in the fire triangle. For example, covering a fire with a fire blanket removes the oxygen part of the triangle and can extinguish a fire.
It starts when a fuel (such as a liquid fuel or flammable gas), oxygen, and heat are mixed in the right proportions and is sparked by something that starts the reaction, such as an electrical spark, mechanical spark, open flame or match. To stop a fire, one of these elements has to be removed from the situation.