Electric fieldAn electric field (sometimes E-field) is the physical field that surrounds electrically charged particles and exerts force on all other charged particles in the field, either attracting or repelling them. It also refers to the physical field for a system of charged particles. Electric fields originate from electric charges and time-varying electric currents. Electric fields and magnetic fields are both manifestations of the electromagnetic field, one of the four fundamental interactions (also called forces) of nature.
EvolutionIn biology, evolution is the change in heritable characteristics of biological populations over successive generations. Evolution occurs when evolutionary processes such as natural selection (including sexual selection) and genetic drift act on genetic variation, resulting in certain characteristics becoming more or less common within a population over successive generations. The process of evolution has given rise to biodiversity at every level of biological organisation.
Productive forcesProductive forces, productive powers, or forces of production (German: Produktivkräfte) is a central idea in Marxism and historical materialism. In Karl Marx and Friedrich Engels' own critique of political economy, it refers to the combination of the means of labor (tools, machinery, land, infrastructure, and so on) with human labour power. Marx and Engels probably derived the concept from Adam Smith's reference to the "productive powers of labour" (see e.g.
Rare diseaseA rare disease is a disease that affects a small percentage of the population. In some parts of the world, an orphan disease is a rare disease whose rarity means there is a lack of a market large enough to gain support and resources for discovering treatments for it, except by the government granting economically advantageous conditions to creating and selling such treatments. Orphan drugs are ones so created or sold. Most rare diseases are genetic in origin and thus are present throughout the person's entire life, even if symptoms do not immediately appear.
Productive and unproductive labourProductive and unproductive labour are concepts that were used in classical political economy mainly in the 18th and 19th centuries, which survive today to some extent in modern management discussions, economic sociology and Marxist or Marxian economic analysis. The concepts strongly influenced the construction of national accounts in the Soviet Union and other Soviet-type societies (see Material Product System).
