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week

(Encyclopedia)week, period of time shorter than the month, commonly seven days. The ancient Egyptians used a 10-day period, as did the French under the short-lived French Revolutionary calendar. In many regions a f...

battery, electric

(Encyclopedia)CE5 Lead storage cell: At the lead-dioxide electrode, electrons from the circuit combine with lead dioxide and sulfuric acid to form lead sulfate and water. At the spongy-lead electrode, lead react...

combustion

(Encyclopedia)combustion, rapid chemical reaction of two or more substances with a characteristic liberation of heat and light; it is commonly called burning. The burning of a fuel (e.g., wood, coal, oil, or natura...

evening star

(Encyclopedia)evening star or morning star, planet that becomes visible in the western sky shortly after sunset or in the eastern sky shortly before sunrise. It can usually be seen in twilight, when it is too light...

oxidation and reduction

(Encyclopedia)oxidation and reduction, complementary chemical reactions characterized by the loss or gain, respectively, of one or more electrons by an atom or molecule. Originally the term oxidation was used to re...

potentiometer

(Encyclopedia)potentiometer. 1 Manually adjustable, variable, electrical resistor. It has a resistance element that is attached to the circuit by three contacts, or terminals. The ends of the resistance element are...

hahnium

(Encyclopedia)hahnium hänˈēəm [key], symbol Ha, former suggested name for both element 105, now called dubnium, and element 108, now called hassium. ...

nielsbohrium

(Encyclopedia)nielsbohrium nēlzbôrˈēəm [key], symbol Ns, former suggested name for both element 105, now called dubnium, and element 107, now called bohrium. ...

Capella, Martianus

(Encyclopedia)Capella, Martianus märshēāˈnəs kəpĕlˈə [key], fl. 5th cent.?, Latin writer, b. Carthage. His one famous work, The Marriage of Mercury and Philology, also called the Satyricon and Disciplinae,...

cornice

(Encyclopedia)cornice kôrˈnĭs [key], molded or decorated projection that forms the crowning feature at the top of a building wall or other architectural element; specifically, the uppermost of the three principa...