A spiro compound, or spirane, is a chemical compound, typically an organic compound, that presents a twisted structure of two or more rings (a ring system), in which 2 or 3 rings are linked together by one common atom.

Bicyclo compounds are a class of saturated compounds consisting of two fused rings, having two or more atoms in common, and that take the name of an open chain hydrocarbon containing the same total number of atoms.

Aromatic compounds are chemical compounds that consist of conjugated planar ring systems accompanied by delocalised pi-electron clouds in place of individual alternating double and single bonds.

Heterocyclic compounds are cyclic compounds with the ring containing carbon and other element, the component being oxygen, nitrogen and sulphur.

The name of is tetrahydro furan. The name of  is furan. The name of  is 2,2,4,4-tetramethylbicyclo[1.1.0]butane. The name of  is 1,2,4,5-tetramethylspiro[2.2]pentane