Oxazines are heterocyclic compounds containing one oxygen and one nitrogen atom in a diunsaturated six-membered ring. The existence of isomers depends on the relative positions of the heteroatoms and the relative positions of the double bonds.
Benzoheterocycles are heterocycles which are fused with a benzene ring. Coumarone, thianaphthene, benzopyridine, isoquinoline, and dibenzopyridine all belong to this class of compounds.