Definition of coke clarifies material composition and commercial varieties relevant to commodity and tax classification today. Definitions of coke describe it as the solid carbonaceous residue left when bituminous coal, petroleum or other liquid hydrocarbons are deprived of volatile constituents by heating in the absence of air. Authoritative dictionaries converge on its identification as a fuel-type residue and note commercial varieties such as pitch coke, petroleum coke and calcined coke, which serve as operative criteria for legal and commodity classification.