A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different elements as members of its ring(s).[Heterocyclic chemistry is the branch of organic chemistry dealing with the synthesis, properties, and applications of these heterocycles.
Examples of heterocyclic compounds include all of the nucleic acids, the majority of drugs, most biomass (cellulose and related materials), and many natural and synthetic dyes.