Bahasa Indonesia adalah bahasa resmi Republik Indonesia^[1] dan bahasa persatuan bangsa Indonesia.^[2] Bahasa Indonesia diresmikan penggunaannya setelah Proklamasi Kemerdekaan Indonesia, tepatnya sehari sesudahnya, bersamaan dengan mulai berlakunya konstitusi. DiTimor Leste, bahasa Indonesia berstatus sebagai bahasa kerja.

In very informal spoken Indonesian, various words are replaced with those of a less formal nature (e.g. tidak (no) is often replaced with the Javanese nggak whilst seperti (like, similar to) is often replaced with kayak (pronounced kai-yah)). As for pronunciation, the diphthongs ai and au on the end of base words are typically pronounced as /e/ and /o/. In informal writing the spelling of words is modified to reflect the actual pronunciation in a way that can be produced with less effort. E.g.: capai becomes cape or capek, pakai become pake, kalau becomes kalo