"Frequently, pyrolyses are s, but... "Pyrolysis" is... broader... [and] more concise. In "decompositions", there is... formation of at least two simpler substances. In pyrolyses... not always... [R]earrangements may be caused by heat alone. ...[F]ormation of large molecules ...is often effected by heat. Both ...are pyrolytic ...but it would be awkward to classify them as decompositions."