Definition - What does Flammable mean?
Flammable can be defined as the ability of any substance or liquid to catch fire and burn on its own. The term is used to label a wide variety of materials and substances that are potent in catching fire. There are flammable liquids such as gasoline that are combustible and have a flashpoint that defines the combustion range. The liquid, in this case, doesn’t catch fire, instead it is the vapor of the liquid that ignites and causes fire.
Petropedia explains Flammable
Oil and natural gas are naturally flammable products, i.e., they are capable of burning. Every flammable liquid has an upper and lower flammable limit that determines its combustion range. Petroleum products such as gasoline, jet fuel, kerosene, diesel, biodiesel, etc., are all flammable and are used to produce energy in various niche applications. Each flammable liquid has a separate flashpoint, autoignition temperature and burns differently under different temperatures. Tests are conducted to detect the degree of flammability of any flammable liquid.