an official language of Indonesia.

only a tiny fraction of the inhabitants of Indonesia speak it as a mother tongue; for most people it is their second language.

phonology and grammar are relatively easy to learn.

the Indonesian name for the language is Bahasa Indonesia (= literally language of Indonesia), and this name is also sometimes used in English.

Bahasa Indonesia is based on Malay, an Austronesian (or Malayo-Polynesian) language which had been used as a lingua franca in the Indonesian archipelago for centuries, and was elevated to the status of official language with the Indonesian declaration of independence in 1945. It is essentially the same language as Bahasa Malaysia, the official language of Malaysia. It is spoken as a mother tongue only by 7% of the population of Indonesia and 45% of the population of Malaysia, but all together almost 200 million people speak it as a second language with varying degrees of proficiency; it is an essential means of communication in a region with more than 300 native languages, used for business and administrative purposes, at all levels of education and in all mass media.

Indonesian is part of the Western Malayo-Polynesian subgroup of the Malayo-Polynesian branch of the Austronesian languages. According to the Ethnologue, Indonesia is modeled after the Riau Malay spoken in northeast Sumatra.

Compared with European languages, Indonesian has a strikingly small use of grammatically gendered words; the same word is used for he and she or for his and her.

Indonesian as a modern dialect of Malay has borrowed heavily from many languages, among others: Sanskrit, Arabic, Portuguese, Dutch, Chinese and many other languages, including other Austronesian languages. It is estimated that there are some 750 Sanskrit loanwords in modern Indonesian, 1000 Arabic (Persian and some Hebrew) ones, some 125 Portuguese (also Spanish and Italian) ones and a staggering number of some 10,000 loanwords from Dutch. The latter also comprises many words from other European languages, which came via Dutch, the so-called "International Vocabulary". The vast majority of Indonesian words, however, come from the root lexical stock of its Austronesian heritage.

Indonesian is written in Latin script and is phonetic, especially since the spelling reform of 1972, which changed spellings based on the Dutch language, such as tj for the sound ch. Another spelling convention that goes back to the Dutch, the use of oe for the sound u, had already been eliminated in 1947, but still survives in proper names, for example Soeharto.