There has for long been discussion among Soviet geographers on the definition of various terms in Soviet usage to indicate the northern part of the USSR. Some of these terms—“the Arctic” [Arktika], “the Arctic region” [arkticheskaya oblast'], “the sub-Arctic” [subarktika], “the polar regions” [Zapolyar'ye]—are normally used to denote areas defined according to physical criteria. Such criteria are similar to those usually applied outside the USSR, such as the “10° C. July isotherm”, the “tree line”, or the “limit of continuous permafrost”, and, again as in the non-Soviet world, the terms have no generally accepted precise meaning and must be defined by each user. But in addition to these terms for natural regions, there are certain terms in predominantly economic and administrative usage: “the north” [sever], “the far north” [dal'niy sever], “the extreme north” [krayniy sever], “the northern marches” [severnyye okrainy], and “the Soviet north” [sovetskiy sever]. Some explanation of their current connotations may be helpful to those studying Soviet literature.