Indonesian (Bahasa Indonesia) is the official and national language of Indonesia. It is a standardized variety of Malay, an Austronesian language that has been used as a lingua franca in the multilingual Indonesian archipelago for centuries. With over 280 million inhabitants, Indonesia ranks as the fourth-most populous nation globally. According to the 2020 census, over 97% of Indonesians are fluent in Indonesian, making it the largest language by number of speakers in Southeast Asia and one of the most widely spoken languages in the world. Indonesian vocabulary has been influenced by various native regional languages such as Javanese, Sundanese, Minangkabau, Balinese, Banjarese, and Buginese, as well as by foreign languages such as Arabic, Dutch, Hokkien, Portuguese, Sanskrit, and English. Most Indonesians, aside from speaking the national language, are fluent in at least one of the more than 700 indigenous local languages; examples include Javanese and Sundanese, which are commonly used at home and within the local community. However, most formal education and nearly all national mass media, governance, administration, and judiciary and other forms of communication are conducted in Indonesian. Under Indonesian rule from 1976 to 1999, Indonesian was designated as the official language of East Timor. It has the status of a working language under the country's constitution along with English. In November 2023, the Indonesian language was recognized as one of the official languages of the UNESCO General Conference. The term Indonesian is primarily associated with the national standard dialect (bahasa baku). However, in a looser sense, it also encompasses the various local varieties spoken throughout the Indonesian archipelago. Standard Indonesian is confined mostly to formal situations, existing in a diglossic relationship with vernacular Malay varieties, which are commonly used for daily communication, coexisting with the aforementioned regional languages and with Malay creoles; standard Indonesian is spoken in informal speech as a lingua franca between vernacular Malay dialects, Malay creoles, and regional languages.

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