Australia is typically regarded as the smallest of the seven continents. The continent of Australia includes only the Australian mainland, and not nearby islands such as Tasmania or New Guinea. From the perspective of geology or physical geography, however, a "continent" may be understood to include the continental shelf (the submerged adjacent area) and the islands on the shelf, which are taken to be structurally part of the continent As Australia the country is mostly on a single landmass, and comprises most of Australia the continent, it is sometimes informally referred to as an "island" continent, surrounded on all sides by oceans. Language spoken is English and major cities are Sydney, Melbourne & Brisbane.