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Letter (alphabet)
A letter is a segmental symbol of a phonemic writing system. The inventory of all letters forms an alphabet. Letters broadly correspond to phonemes in the spoken form of the language, although there is rarely a consistent and exact correspondence between letters and phonemes. The word ''letter'', borrowed from Old French ''letre'', entered Middle English around 1200 AD, eventually displacing the Old English term ( bookstaff). ''Letter'' is descended from the Latin '' littera'', which may have descended from the Greek "διφθέρα" (, writing tablet), via Etruscan. Definition and usage A letter is a type of grapheme, which is a functional unit in a writing system: a letter (or group of letters) represents visually a phoneme (a unit of sound that can distinguish one word from another in a particular language). Letters are combined to form written words, just as phonemes are combined to form spoken words. A sequence of graphemes representing a phoneme is called a multi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Symbol
A symbol is a mark, sign, or word that indicates, signifies, or is understood as representing an idea, object, or relationship. Symbols allow people to go beyond what is known or seen by creating linkages between otherwise very different concepts and experiences. All communication (and data processing) is achieved through the use of symbols. Symbols take the form of words, sounds, gestures, ideas, or visual images and are used to convey other ideas and beliefs. For example, a red octagon is a common symbol for "STOP"; on maps, blue lines often represent rivers; and a red rose often symbolizes love and compassion. Numerals are symbols for numbers; letters of an alphabet may be symbols for certain phonemes; and personal names are symbols representing individuals. The variable 'x', in a mathematical equation, may symbolize the position of a particle in space. The academic study of symbols is semiotics. In cartography, an organized collection of symbols forms a legend for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trigraph (orthography)
A trigraph (from the el, τρεῖς, ''treîs'', "three" and γράφω, ''gráphō'', "write") is a group of three characters used to represent a single sound or a combination of sounds that does not correspond to the written letters combined. Latin-script trigraphs For example, in the word '' schilling'', the trigraph ''sch'' represents the voiceless postalveolar fricative , rather than the consonant cluster . In the word ''beautiful,'' the sequence ''eau'' is pronounced , and in the French word ''château'' it is pronounced . It is sometimes difficult to determine whether a sequence of letters in English is a trigraph, because of the complicating role of silent letters. There are however a few productive trigraphs in English such as ''tch'' as in ''watch,'' and ''igh'' as in ''high.'' The trigraph ''sch'' in German is equivalent to the English ''sh'' and pronounced . In Dutch, which is closely related to German, this same trigraph is pronounced . In Italian, however, ''sch'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gamma Ray
A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically shorter than those of X-rays. With frequencies above 30 exahertz (), it imparts the highest photon energy. Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900 while studying radiation emitted by radium. In 1903, Ernest Rutherford named this radiation ''gamma rays'' based on their relatively strong penetration of matter; in 1900 he had already named two less penetrating types of decay radiation (discovered by Henri Becquerel) alpha rays and beta rays in ascending order of penetrating power. Gamma rays from radioactive decay are in the energy range from a few kiloelectronvolts (keV) to approximately 8 megaelectronvolts (MeV), corresponding to the typical energy levels in nuclei with reasonably long lif ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beta Ray
A beta particle, also called beta ray or beta radiation (symbol β), is a high-energy, high-speed electron or positron emitted by the radioactive decay of an atomic nucleus during the process of beta decay. There are two forms of beta decay, β− decay and β+ decay, which produce electrons and positrons respectively. Beta particles with an energy of 0.5 MeV have a range of about one metre in air; the distance is dependent on the particle energy. Beta particles are a type of ionizing radiation and for radiation protection purposes are regarded as being more ionising than gamma rays, but less ionising than alpha particles. The higher the ionising effect, the greater the damage to living tissue, but also the lower the penetrating power of the radiation. Beta decay modes β− decay (electron emission) An unstable atomic nucleus with an excess of neutrons may undergo β− decay, where a neutron is converted into a proton, an electron, and an electron antineutrino (the anti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alpha Ray
Alpha particles, also called alpha rays or alpha radiation, consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus. They are generally produced in the process of alpha decay, but may also be produced in other ways. Alpha particles are named after the first letter in the Greek alphabet, α. The symbol for the alpha particle is α or α2+. Because they are identical to helium nuclei, they are also sometimes written as or indicating a helium ion with a +2 charge (missing its two electrons). Once the ion gains electrons from its environment, the alpha particle becomes a normal (electrically neutral) helium atom . Alpha particles have a net spin of zero. Due to the mechanism of their production in standard alpha radioactive decay, alpha particles generally have a kinetic energy of about 5 MeV, and a velocity in the vicinity of 4% of the speed of light. (See discussion below for the limits of these figures in alpha decay.) They a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Federal Bureau Of Investigation
The Federal Bureau of Investigation (FBI) is the domestic intelligence and security service of the United States and its principal federal law enforcement agency. Operating under the jurisdiction of the United States Department of Justice, the FBI is also a member of the U.S. Intelligence Community and reports to both the Attorney General and the Director of National Intelligence. A leading U.S. counterterrorism, counterintelligence, and criminal investigative organization, the FBI has jurisdiction over violations of more than 200 categories of federal crimes. Although many of the FBI's functions are unique, its activities in support of national security are comparable to those of the British MI5 and NCA; the New Zealand GCSB and the Russian FSB. Unlike the Central Intelligence Agency (CIA), which has no law enforcement authority and is focused on intelligence collection abroad, the FBI is primarily a domestic agency, maintaining 56 field offices in major cities t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Letters Used In Mathematics And Science
:''This list is about the meanings of the letters used in mathematics, science and engineering. SI units are indicated in parentheses. For the Unicode blocksee Mathematical Alphanumeric Symbols.'' Latin and Greek letters are used in mathematics, science, engineering, and other areas where mathematical notation is used as symbols for constants, special functions, and also conventionally for variables representing certain quantities. :Some common conventions: * Intensive quantities in physics are usually denoted with minusculeswhile extensive are denoted with capital letters. * Most symbols are written in italics. * Vectors can be denoted in boldface. * Sets of numbers are typically bold or blackboard bold. Latin Greek More See also * Blackboard bold letters used in mathematics * Greek letters used in mathematics, science, and engineering * Latin letters used in mathematics Many letters of the Latin alphabet, both capital and small, are used in mathematics, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arabic Numerals
Arabic numerals are the ten numerical digits: , , , , , , , , and . They are the most commonly used symbols to write decimal numbers. They are also used for writing numbers in other systems such as octal, and for writing identifiers such as computer symbols, trademarks, or license plates. The term often implies a decimal number, in particular when contrasted with Roman numerals. They are also called Western Arabic numerals, Ghubār numerals, Hindu-Arabic numerals, Western digits, Latin digits, or European digits. The '' Oxford English Dictionary'' differentiates them with the fully capitalized ''Arabic Numerals'' to refer to the Eastern digits. The term numbers or numerals or digits often implies only these symbols, however this can only be inferred from context. It was in the Algerian city of Béjaïa that the Italian scholar Fibonacci first encountered the numerals; his work was crucial in making them known throughout Europe. European trade, books, and colonialism he ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Roman Numerals
Roman numerals are a numeral system that originated in ancient Rome and remained the usual way of writing numbers throughout Europe well into the Late Middle Ages. Numbers are written with combinations of letters from the Latin alphabet, each letter with a fixed integer value, modern style uses only these seven: The use of Roman numerals continued long after the decline of the Roman Empire. From the 14th century on, Roman numerals began to be replaced by Arabic numerals; however, this process was gradual, and the use of Roman numerals persists in some applications to this day. One place they are often seen is on clock faces. For instance, on the clock of Big Ben (designed in 1852), the hours from 1 to 12 are written as: The notations and can be read as "one less than five" (4) and "one less than ten" (9), although there is a tradition favouring representation of "4" as "" on Roman numeral clocks. Other common uses include year numbers on monuments and buildings and co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Code Point
In character encoding terminology, a code point, codepoint or code position is a numerical value that maps to a specific character. Code points usually represent a single grapheme—usually a letter, digit, punctuation mark, or whitespace—but sometimes represent symbols, control characters, or formatting. The set of all possible code points within a given encoding/character set make up that encoding's ''codespace''. For example, the character encoding scheme ASCII comprises 128 code points in the range 0 hex to 7Fhex, Extended ASCII comprises 256 code points in the range 0hex to FFhex, and Unicode comprises code points in the range 0hex to 10FFFFhex. The Unicode code space is divided into seventeen planes (the basic multilingual plane, and 16 supplementary planes), each with (= 216) code points. Thus the total size of the Unicode code space is 17 × = . Definition The notion of a code point is used for abstraction, to distinguish both: * the numbe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Latin Alphabet
The Latin alphabet or Roman alphabet is the collection of letters originally used by the ancient Romans to write the Latin language. Largely unaltered with the exception of extensions (such as diacritics), it used to write English and the other modern European languages. With modifications, it is also used for other alphabets, such as the Vietnamese alphabet. Its modern repertoire is standardised as the ISO basic Latin alphabet. Etymology The term ''Latin alphabet'' may refer to either the alphabet used to write Latin (as described in this article) or other alphabets based on the Latin script, which is the basic set of letters common to the various alphabets descended from the classical Latin alphabet, such as the English alphabet. These Latin-script alphabets may discard letters, like the Rotokas alphabet, or add new letters, like the Danish and Norwegian alphabets. Letter shapes have evolved over the centuries, including the development in Medieval Latin of lower-c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
