Indonesia is the world's largest island country and the 14th largest country by land area, at 1,904,569 square kilometres (735,358 square miles). With over 267 million people, it is the world's 4th-most populous country as well as the most populous Muslim-majority country. Java, the world's most populous island, is home to more than half of the country's population. The capital Jakarta is home to Istiqlal Mosque, the largest mosque in Southeast Asia.

The name Indonesia derives from Greek words of "Indos" and "nesos", meaning "Indian islands". The name dates to the 18th century, far predating the formation of independent Indonesia.

The official language is Indonesian (locally known as "bahasa Indonesia"), a standardised form of Malay, which serves as the lingua franca (a bridge or common language) of the archipelago. More than 700 living languages are spoken in Indonesia. Which indicates it has about 10% of the world’s languages, establishing its reputation as the second most linguistically diverse nation in the world after Papua New Guinea. Most languages belong to the Austronesian language family, while there are over 270 Papuan languages spoken in eastern Indonesia.

- Japan is the second largest island country in the world by population and fourth by surface area.

- Madagascar is the second largest island country in the world by surface area and fifth by population.

- Greenland is the largest island in the world but is not a country.

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