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thunderstorm

(Encyclopedia)thunderstorm, violent, local atmospheric disturbance accompanied by lightning, thunder, and heavy rain, often by strong gusts of wind, and sometimes by hail. The typical thunderstorm caused by convect...

pole, in electricity and magnetism

(Encyclopedia)pole, in electricity and magnetism, point where electric or magnetic force appears to be concentrated. A single electric charge located at a point is sometimes referred to as an electric monopole. An ...

dragonfly

(Encyclopedia)dragonfly, any insect of the order Odonata, which also includes the damselfly. Members of this order are generally large predatory insects and characteristically have chewing mouthparts and four membr...

Wegener, Alfred Lothar

(Encyclopedia)Wegener, Alfred Lothar älˈfrĕt lōtärˈ vĕgˈənər [key], 1880–1930, German geologist, meteorologist, and Arctic explorer. Early in his life, he was on the staff of the aeronautical observator...

Urals

(Encyclopedia)Urals or Ural Mountains, E European Russia and NW Kazakhstan, forming, together with the Ural River, the traditional boundary between Europe and Asia and separating the Russian plain from the W Siberi...

Narmada

(Encyclopedia)Narmada nərmŭˈdə [key], river, c.775 mi (1,250 km) long, rising in Madhya Pradesh state, central India, and flowing W between the Satpura and Vindhya ranges through Gujarat state to the Gulf of Kh...

bee fly

(Encyclopedia)bee fly, name for the small- to medium-sized flies of the family Bombyliidae, many of which resemble bees in appearance and behavior. This mimicry provides bee flies with some measure of protection ag...

Prometheus, in Greek mythology

(Encyclopedia)Prometheus prōmēˈthēəs [key], in Greek mythology, great benefactor of mankind. He was the son of the Titan Iapetus and of Clymene or Themis. Because he foresaw the defeat of the Titans by the Oly...

Hohokam

(Encyclopedia)Hohokam hōˈhōkămˌ, hōhōˈkəm [key], term denoting the culture of the ancient agricultural populations inhabiting the Salt and Gila river valleys of S Arizona (a.d. 300–1200). They are noted ...

pine nut

(Encyclopedia)pine nut or piñon pĭnˈyən, pēˈnyōn [key], edible seed of various species of pine trees. Among the North American species that bear such edible seeds are the nut pines or piñons, Pinus edulis a...