Originally, a very large contiguous landmass on Old Earth, separated or largely separated from other continents by ocean. By common convention, Asia, Africa, North America, South America, Antarctica, Europe, and Australia were regarded as continents, though some preferred to regard Europe as a subcontinent of a larger Eurasian continent. Land masses smaller than Australia, such as Greenland or New Guinea, were somewhat arbitrarily regarded as large islands.
Some Gaian class worlds, some terraformed worlds, and some extremely large habitats such as Banks Orbitals may also have land masses that are regarded by their inhabitants as continents. In such places, as on Old Earth, the designation of a geographic continent is more a matter of convention than definition. The geological definition of a continent is somewhat less subject to cultural interpretation.