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Possible definitions for radii

radio
Electromagnetic radiation of lower frequency (hence longer wavelength) than visible light or infrared radiation, and consisting of the range of frequencies used for navigation signals, AM and FM broadcasting, television transmissions, cell-phone communications, and various forms of radar. For radio transmission, information is imparted to a carrier wave by varying (modulating) its amplitude, frequency, or duration. The technology of radio arose from the work of M. Faraday, J. C. Maxwell, H. Hertz, G. Marconi, and others, and improvement followed the development of the vacuum tube, the electronic-tube oscillator, the tuned circuit, and other components. Later innovations have included the replacement of tubes by transistors and of wires by printed circuits. See also radio and radar astronomy.


radish
Annual or biennial plant (Raphanus sativus) of the mustard family, probably of Oriental origin, grown for its large, succulent root. Low in calories and high in bulk, radishes have a sharp taste and are usually eaten raw. The shape of the edible portion of the root varies greatly, as does the color (from white through pink to red, purple, and black). Radishes may weigh only a few ounces (U.S. and European varieties) or, in the case of the Japanese daikon, more than 2 lbs (1 kg).


radium
Chemical element, heaviest alkaline earth metal, chemical symbol Ra, atomic number 88. It was discovered by M. and P. Curie in 1898 and isolated by 1910. All its isotopes are radioactive (see radioactivity). Radium does not occur free in nature but occurs in natural ores such as pitchblende as a disintegration product of radioactive decay of heavier elements, incl. uranium. Its use in medicine (see radiation therapy, radiology, nuclear medicine) has declined because of its cost, and its use in consumer goods (to illuminate watch and clock hands and numbers, as well as instrument dials) was halted because it can cause radiation injury. It is still used for some radiography and as a source of neutrons.


Hadith
In Islam, the oral traditions attributed to the Prophet Muhammad, his family, and the Companions of the Prophet. Hadith is revered by Muslims as a major source of religious law and moral guidance. It consists of two parts: the oral law itself and the isnad, or chain of authorities who passed it down to posterity. The various collections of Hadith provide the major source for studying the development of Islam in its first few centuries.


Hadrian
Roman emperor (117-38), Trajan's nephew and successor. After years of intrigue, he was adopted and named successor just before Trajan's death. He executed his senatorial opponents, abandoned Trajan's conquests in Armenia and Mesopotamia, and coped with unrest in Mauretania and Parthia. He traveled widely, and many of his accomplishments were related to his visits abroad. He began construction of Hadrian's Wall, and he visited and ...

Top words beginning with R: redtailed, retrust, raveled, resubscribing, reverbrate, refilters, respirator, resipsy, refiners, redisseizor, reingress, reassemblies, rookeries, roms, raylike, redreamt, raviolis, rerecords, rolleywayman, ringleted

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