An IETF language tag is an abbreviated language code (for example, en for English, pt-BR for Brazilian Portuguese, or nan-Hant-TW for Min Nan Chinese as spoken in Taiwan using traditional Han characters) defined by the Internet Engineering Task Force (IETF) in the BCP 47 document series, which is currently composed of normative RFC 5646 (referencing the related RFC 5645) and RFC 4647, along with the normative content of the IANA Language Subtag Registry. Components of language tags are drawn from ISO 639, ISO 15924, ISO 3166-1, and UN M.49.