Desertification has been defined by the United Nations Environment Programme (UNEP) as land degradation in arid, semi-arid, and dry subhumid areas resulting mainly from adverse human impact. This 1991 definition is a revision of the definition formulated at the 1977 United Nations Conference on Desertification. The 1977 definition described desertification as the diminution or destruction of the biological potential of the land, which could lead ultimately to the formation of desert-like conditions (UNCOD 1977).

Indicators: Signals of processes, inputs, outputs, effects, results outcomes, impacts etc.. that enable such phenomena to be judged or measured (FAO, 1997).

Land is a delineable area of the earth's terrestrial surface, encompassing all attributes of the biosphere immediately above or below this surface, including those of the near surgface climate, the soil and terrain forms, the surface hydrology , the near surface sedimentary layersand associated ground water reserve, the plant and animal population, the human settlement pattern and physical results of past and present human activity (FAO, 1995).

Land Cover is the observed (bio)physical cover of the earth's surface (FAO, 1997).

Land Degradation implies reduction of resource potential by one or a combination of processes acting on the land. These processes include water erosion, wind erosion and sedimentation by those agents, long-term reduction in the amount or diversity of natural vegetation, where relevant, and salinization and sodication" (UNEP, 1992).
Degraded land has been defined as land which due to natural processes or human activity no longer is able to sustain properly an economic function and/or the original ecological function (ISO, 1996).

Land Use is characterized by the arrangement, activities and inputs people undertake in a certain land cover type to produce, change or maintain it (FAO, 1997).

Soil Degradation characterized by the decline in soil qualities coomonly caused by the improper use by humans (ISSS, 1996).

Publication: Terminology for Integrated Resources Planning and Management