Australia is a continent comprising mainland Australia, Tasmania, New Guinea, Seram, possibly Timor, and neighbouring islands. The continent is sometimes known in technical contexts by the names Sahul, Australinea or Meganesia, to distinguish it from the Australian mainland. It is the smallest of the seven traditional continents in the English conception. New Zealand is not part of the continent of Australia, but of the separate, submerged continent of Zealandia. Zealandia and Australia are both part of the wider regions known as Australasia and Oceania.
The continent of Australia lies on a continental shelf overlain by shallow seas which divide it into several landmasses — the Arafura Sea and Torres Strait between mainland Australia and New Guinea, and Bass Strait between mainland Australia and Tasmania. When sea levels were lower during the Pleistocene ice age, including the last glacial maximum about 18,000 BC, they were connected by dry land. During the past ten thousand years, rising sea levels overflowed the lowlands and separated the continent into today's low-lying arid to semi-arid mainland and the two mountainous islands of New Guinea and Tasmania. Geologically, a continent extends to the edge of its continental shelf, so the now-separate islands are considered part of the continent. Due to the spread of animals, fungi and plants across the single Pleistocene landmass the separate lands have a related biota.