iupac

As a proper noun iupac

is (chemistry) : an organization that establishes official names of chemical elements and compounds.

As an adjective undefined is

lacking a definition or value.

Wikidiffcom is likely misspelled.

Wikidiffcom has no English definition.

As a proper noun IUPAC is

acronym of International Union of Pure and Applied Chemistry|lang=en: an organization that establishes official names of chemical elements and compounds.

As a noun taxonomy

is the science or the technique used to make a classification.

As a proper noun iupac is

(chemistry) : an organization that establishes official names of chemical elements and compounds.