Australia /ɒˈstreɪliə/, /ə-/, or colloquially /-jə/,[10][11] officially the Commonwealth of Australia,[12] is a country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. It is the world's sixth-largest country by total area. Neighbouring countries include Indonesia, East Timor and Papua New Guinea to the north; the Solomon Islands and Vanuatu to the north-east; and New Zealand to the south-east.