The "preferred IUPAC nomenclature" provides a set of rules for choosing between multiple possibilities in situations where it is important to decide on a unique name.
[1] Preferred IUPAC names are applicable only for organic compounds, to which the IUPAC (International Union of Pure and Applied Chemistry) has the definition as compounds which contain at least a single carbon atom but no alkali, alkaline earth or transition metals and can be named by the nomenclature of organic compounds[2] (see below).
[3] The concept of PINs is defined in the introductory chapter and chapter 5 of the "Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013" (freely accessible),[4] which replace two former publications: the "Nomenclature of Organic Chemistry", 1979 (the Blue Book) and "A Guide to IUPAC Nomenclature of Organic Compounds, Recommendations 1993".
[7] A preselected name is not necessarily a PIN in inorganic chemical nomenclature.
The systems of chemical nomenclature developed by the International Union of Pure and Applied Chemistry (IUPAC) have traditionally concentrated on ensuring that chemical names are unambiguous, that is that a name can only refer to one substance.
[8] The nomenclature goes:[9] The following are available, but not given special preference:[10] The number of retained non-systematic, trivial names of simple organic compounds (for example formic acid and acetic acid) has been reduced considerably for preferred IUPAC names, although a larger set of retained names is available for general nomenclature.