This document provides the harmonized terminology and general principles of language coding for the language code elements originally specified by the parts of the ISO 639 series. It provides rules for the selection, formation, presentation and use of language identifiers as well as language reference names. It also provides principles, rules and guidelines for the selection, formation and presentation of alternate language names in the official ISO languages English and French. Furthermore, principles, rules and guidelines are provided for the adoption of standardized language code elements using language names other than English or French. In addition, this document lays down guidelines for the use of language identifiers and describes their possible combination with identifiers of other codes. The terminology as well as the principles, rules and guidelines provided in this document set the framework for the ISO 639/MA Terms of Reference (ISO 639/MA-ToR) for the maintenance of the language code. This document was developed in close coordination with ISO/DTR 21636, in particular with respect to clause 3.