What is "flammability"

Flammability \Flam`ma*bil"ity\, n. The quality of being flammable; inflammability. [Obs.]
--Sir T. Browne.

n. 1 (context uncountable English) The condition of being flammable 2 (context countable English) A measure of the extent to which something is flammable

Flammability is the ability of a substance to burn or ignite, causing fire or combustion. The degree of difficulty required to cause the combustion of a substance is quantified through fire testing. Internationally, a variety of test protocols exist to quantify flammability. The ratings achieved are used in building codes, insurance requirements, fire codes and other regulations governing the use of building materials as well as the storage and handling of highly flammable substances inside and outside of structures and in surface and air transportation. For instance, changing an occupancy by altering the flammability of the contents requires the owner of a building to apply for a building permit to make sure that the overall fire protection design basis of the facility can take the change into account.