Pyrone

noun

1. A crystalline ketonic compound, C5H4O2, made by heating chelidonic acid. It melts at 32.5° C.
2. An unsaturated cyclic compound, C5H4O2, of which two varieties are known, α and γ. γ-pyrone is the parent substance of several natural yellow dyestuffs.
3. Any of a class of cyclic chemical compounds that contain an unsaturated six-membered ring with two double bonds, one oxygen atom and a ketone functional group.