What is the measure of whether or not a material will burn?

Combustibility is the correct measure of whether or not a material will burn. It refers specifically to a substance's ability to ignite and sustain combustion when exposed to an ignition source. This characteristic is essential for firefighters to understand, as it influences how materials will react in a fire situation, including their flammability and how they might contribute to fire spread.

Conductivity pertains to how well a material can conduct electricity or heat, which does not directly indicate its ability to catch fire. Thermability is not a standard term associated with fire behavior and thus does not accurately describe the burning properties of materials. Reducibility is related to the capacity of substances to be reduced in chemical reactions, but this term does not address the flame characteristics relevant to combustibility. Thus, combustibility is the key concept that determines whether a material can sustain combustion and contribute to fire dynamics.