Generally, the world's natural resources as handed down to the present generation, and specifically, the earth's outstanding physical, biological and geological formations, and habitats of threatened species of animals and plants and areas with scientific, conservation or aesthetic value. (Source: GEMET/WHC / OED)

Natural features consisting of physical and biological formations or groups of such formations, which are of outstanding universal value from the aesthetic or scientific point of view; geological and physiographical formations and precisely delineated areas which constitute the habitat of threatened species of animals and plants of outstanding universal value from the point of view of science or conservation; natural sites or precisely delineated natural areas of outstanding universal value from the point of view of science, conservation or natural beauty. (Source: Art. World Heritage Convention)