Agriculture (a term which encompasses farming) is the art, science or practice of producing food, feed, fiber and many other desired goods by the systematic raising of plants and animals. Agri is from Latin ager ("a field"), and culture is from Latin cultura, meaning "cultivation" in the strict sense of tillage of the soil. Thus a literal reading of the English word yields tillage of the soil of a field. In actual usage, Agriculture denotes a broad array of activities essential to food and material production, including all techniques for raising and processing livestock (see Animal husbandry) no less than those essential to crop planting and harvesting.
Continual improvement in agricultural methods from pre-history to the present has been the key factor in the extreme specialization of human activity during the historical epoch. Many of these specializations have nothing to do with food production, but when specialists such as scientists, inventors and mechanical and chemical engineers devote their efforts to the improvement of farming methods, resources and implements they too, along with those who work the fields and pens, are said to be "in agriculture".
42% (2002 estimate) of the world's population is employed in agriculture, making it by far the most common occupation, yet it accounts for only 4.4% (2005 estimate) of the Gross World Product (an aggregate of all Gross Domestic Products).*