These words are all used to describe material that can catch fire. Combustible is the most formal term here and also the most neutral in simply denoting material that will burn easily: Combustible building materials such as laths have been replaced by highly fire-resistant materials such as asbestos fibre-board.

Burnable is at the other end of the scale from combustible in its relaxed, almost slangy tone. It is also less neutral in pointing to a desired or desirable quality: Boy Scouts scouring the scrub for every burnable stick of firewood.

Inflammable and flammable are identical in meaning and are frequently used as warning signs to label hazardous material that may result in unwanted fires unless handled with caution: Combustible substances such as phosphorus must not be shipped without "flammable " clearly written across the container. Flammable has begun to replace inflammable as the word of warning, primarily because to many people confused inflammable with its opposite, non-flammable.