A barren treeless region usually north of the 10 °C isotherm, north of which the mean temperature of the warmest month falls below that value and tree growth ceases to be possible, but also sometimes applied to alpine tundras. Characterised by very low winter temperatures, short cool summers, permafrost below a surface layer subject to summer melt and dominated by lichens, mosses and low shrubs.

Alternative form for tundra : tundras.