In physical geography, tundra (/ˈtʌndrə, ˈtʊn-/) is a type of biome where the tree growth is hindered by low temperatures and short growing seasons. The term tundra comes through Russian тундра (tûndra) from the Kildin Sámi word тӯндар (tūndâr) meaning "uplands", "treeless mountain tract". Tundra vegetation is composed of dwarf shrubs, sedges and grasses, mosses, and lichens. Scattered trees grow in some tundra regions. The ecotone (or ecological boundary region) between the tundra and the forest is known as the tree line or timberline.