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8 ( eight ) is the following 7 and preceding 9.


In mathematics
8 is:
  • a , its being , , and . It is twice 4 or four times 2.
  • a power of two, being 2 (two cubed), and is the first number of the form , being an integer greater than 1.
  • the first number which is neither nor .
  • the base of the number system, which is mostly used with . In octal, one digit represents three . In modern computers, a is a grouping of eight bits, also called an .
  • a , being plus . The next Fibonacci number is . 8 is the only positive Fibonacci number, aside from 1, that is a perfect cube.Bryan Bunch, The Kingdom of Infinite Number. New York: W. H. Freeman & Company (2000): 88
  • the only nonzero that is one less than another perfect power, by Mihăilescu's Theorem.
  • the order of the smallest non-abelian group all of whose subgroups are normal.
  • the dimension of the and is the highest possible dimension of a normed division algebra.
  • the first number to be the aliquot sum of two numbers other than itself; the discrete biprime , and the square number .

A number is divisible by 8 if its last three digits, when written in , are also divisible by 8, or its last three digits are 0 when written in .

There are a total of eight convex .

A with eight sides is an . representing octagons (including eight) are called .

A with eight faces is an . A has as faces six equal squares and eight equal regular triangles.

A has eight vertices.

always have exactly eight divisors.

The number 8 is involved with a number of interesting mathematical phenomena related to the notion of Bott periodicity. For example, if O(∞) is the direct limit of the inclusions of real orthogonal groups

O(1)\hookrightarrow O(2)\hookrightarrow\ldots\hookrightarrow O(k)\hookrightarrow\ldots,
then
\pi_{k+8}(O(\infty))\cong\pi_{k}(O(\infty)).

Clifford algebras also display a periodicity of 8. For example, the algebra Cl( p + 8, q) is isomorphic to the algebra of 16 by 16 matrices with entries in Cl( p, q). We also see a period of 8 in the of spheres and in the representation theory of the rotation groups, the latter giving rise to the 8 by 8 chessboard. All of these properties are closely related to the properties of the .

The Spin(8) is the unique such group that exhibits the phenomenon of .

The lowest-dimensional even unimodular lattice is the 8-dimensional E8 lattice. Even positive definite unimodular lattices exist only in dimensions divisible by 8.

A figure 8 is the common name of a , often used in the context of sports, such as skating. Figure-eight turns of a rope or cable around a cleat, pin, or bitt are used to belay something.


List of basic calculations
8 × x81624324048566472808896104112120

8 ÷ x842.21.61.1.10.0.8 !0.0.0.0.0.5
x ÷ 80.1250.250.3750.50.6250.750.87511.1251.25 !1.3751.51.6251.751.875

88645124096327682621442097152167772161342177281073741824 !858993459268719476736549755813888
x1256656165536390625167961657648011677721643046721100000000 !214358881429981696815730721


Etymology
English eight, from Old English eahta, æhta, *ahto is a direct continuation of Proto-Indo-European , and as such cognate with Greek ὀκτώ and Latin octo-, both of which stems are reflected by the English prefix , as in the ordinal adjective octaval or octavary, the distributive adjective is . The adjective octuple (Latin octu-plus) may also be used as a noun, meaning "a set of eight items"; the diminutive is mostly used to refer to eight sibling delivered in one birth.

The is based on a root *θmn-, whence Akkadian smn-, Arabic ṯmn-, Hebrew šmn- etc.

The , written 八 (Mandarin: ; Cantonese: baat), is from *priāt-, ultimately from Sino-Tibetan which also yielded Tibetan .

It has been argued that, as the cardinal number is the highest number of item that can universally be cognitively processed as a single set, the etymology of the numeral eight might be the first to be considered composite, either as "twice four" or as "two short of ten", or similar. The words for "eight" are from a stem *sekiz, which has been suggested as originating as a negation of eki "two", as in "without two fingers" (i.e., "two short of ten; two fingers are not being held up"); Etymological Dictionary of Turkic Languages: Common Turkic and Interturkic stems starting with letters «L», «M», «N», «P», «S», Vostochnaja Literatura RAS, 2003, 241f. ( altaica.ru) this same principle is found in , which conveys a meaning of "two before (ten)". The Proto-Indo-European reconstruction itself has been argued as representing an old dual, which would correspond to an original meaning of "twice four". Proponents of this "quaternary hypothesis" adduce the numeral , which might be built on the stem new-, meaning "new" (indicating the beginning of a "new set of numerals" after having counted to eight).the hypothesis is discussed critically (and rejected as "without sufficient support") by Werner Winter, 'Some thought about Indo-European numerals' in: Jadranka Gvozdanović (ed.), Indo-European Numerals, Walter de Gruyter, 1992, 14f.


Glyph
The modern 8 glyph, like all modern Hindu-Arabic numerals (other than zero) originates with the . The Brahmi numeral for eight by the 1st century was written in one stroke as a curve └┐ looking like an uppercase H with the bottom half of the left line and the upper half of the right line removed. However the eight glyph used in India in the early centuries of the Common Era developed considerable variation, and in some cases took the shape of a single wedge, which was adopted into the Perso-Arabic tradition as (and also gave rise to the later Devanagari numeral ; the alternative curved glyph also existed as a variant in Perso-Arabic tradition, where it came to look similar to our glyph 5.

The numerals as used in by the 10th century were a distinctive western variant of the glyphs used in the Arabic-speaking world, known as ghubār numerals ( ghubār translating to ""). In these numerals, the line of the 5-like glyph used in Indian manuscripts for eight came to be formed in ghubār as a closed loop, which was the 8-shape that became adopted into European use in the 10th century.Georges Ifrah, The Universal History of Numbers: From Prehistory to the Invention of the Computer transl. David Bellos et al. London: The Harvill Press (1998): 395, Fig. 24.68.

Just as in most modern , in typefaces with the 8 character usually has an ascender, as, for example, in .

The ∞, described as a "sideways figure eight" is unrelated to the 8 glyph in origin; it is first used (in the mathematical meaning "infinity") in the 17th century, and it may be derived from the for "one thousand" CIƆ, or alternatively from the final Greek letter, ω.

The numeral eight in , developed in by the 5th century BC, was written as Η, the eighth letter of the Greek alphabet.

The eight is written in two strokes, 八]]; the glyph is also the 12th .


In science

Physics
  • In nuclear physics, the second magic number.
  • In , the eightfold way is used to classify sub-atomic particles.
  • In statistical mechanics, the eight-vertex model has 8 possible configurations of arrows at each vertex.


Astronomy


Chemistry
  • The of .
  • The number of allotropes of carbon.
  • The most stable allotrope of a molecule is made of eight sulfur atoms arranged in a rhombic form.
  • The maximum number of electrons that can occupy a valence shell.
  • The red pigment consists of eight units.


Geology
  • A crystal is bounded by eight scalene triangles arranged in pairs. A ditetragonal prism in the tetragonal crystal system has eight similar faces whose alternate interfacial angles only are equal.


Biology
  • All , and more generally all , have eight legs. Orb-weaver spiders of the cosmopolitan family Areneidae have eight similar eyes.
  • The and its cephalopod relatives in genus Argonauta have eight arms (tentacles).
  • Compound coelenterates of the subclass or order have polyps with eight-branched tentacles and eight septa.
  • Sea anemones of genus have eight mesenteries.
  • Animals of phylum swim by means of eight meridional bands of transverse ciliated plates, each plate representing a row of large modified cilia.
  • The eight-spotted forester (genus Alypia, family ) is a diurnal moth having black wings with brilliant white spots.
  • The in fungi of the class Ascomycetes, following nuclear fusion, bears within it typically eight ascospores.
  • Herbs of genus (tickseed) have showy flower heads with involucral bracts in two distinct series of eight each.
  • identified a hierarchy of eight levels of consciousness.
  • In human there are eight teeth in each quadrant. The eighth tooth is the so-called .
  • There are eight on each side in man and most mammals.


In technology
  • A is eight .
  • Many (mostly historic) computer architectures are eight-bit, among them the Nintendo Entertainment System.
  • Standard-8 and Super-8 are 8 mm film formats.
  • Video8, Hi8 and Digital8 are related 8 mm video formats.
  • On most phones, the 8 key is associated with the letters T, U, and V, but on the it is the key for B, N, and X.
  • An eight may refer to an eight-cylinder engine or automobile. A V8 engine is an internal combustion engine with eight cylinders configured in two banks (rows) of four forming a "V" when seen from the end.
  • A figure-eight knot (so named for its configuration) is a kind of .
  • The number eight written in parentheses is the code for the musical note in Windows Live Messenger.
  • In a seven-segment display, when an 8 is illuminated, all the display bulbs are on.


In measurement
  • The for 10008 is yotta (Y), and for its reciprocal, yocto (y).
  • In liquid measurement (United States customary units), there are eight in a cup, eight in a and eight in a gill.
  • There are eight in a mile.
  • The clove, an old English unit of weight, was equal to eight pounds when measuring cheese.
  • An eight may be an article of clothing of the eighth .
  • Force eight is the first strength attributed to a on the when announced on a Shipping Forecast.


In culture

Architecture
  • Various types of buildings are usually eight-sided (octagonal), such as single-roomed and multi-roomed (descended from stupas; see religion section below).
  • Eight caulicoles rise out of the leafage in a , ending in leaves that support the .


In religion, folk belief and divination

Buddhism
  • The , a symbol, has eight spokes. The Buddha's principal teaching—the Four Noble Truths—ramifies as the Noble Eightfold Path and the Buddha emphasizes the importance of the eight attainments or jhanas.
  • In Buddhism, the branches of the Eightfold Path are embodied by the Eight Great Bodhisattvas: (, , Avalokiteśvara, , , Nivaranavishkambhi, , and ). These are later (controversially) associated with the Eight Consciousnesses according to the school of thought: consciousness in the five senses, thought-consciousness, self-consciousness, and unconsciousness-"consciousness" or "store-house consciousness" (alaya-vijñana). The "irreversible" state of enlightenment, at which point a Bodhisattva goes on "autopilot", is the Eight Ground or bhūmi. In general, "eight" seems to be an auspicious number for Buddhists, e.g., the "eight auspicious symbols" (the jewel-encrusted parasol; the goldfish (always shown as a pair, e.g., the glyph of Pisces); the self-replenishing amphora; the white kamala lotus-flower; the white conch; the eternal (Celtic-style, infinitely looping) knot; the banner of imperial victory; the eight-spoked wheel that guides the ship of state, or that symbolizes the Buddha's teaching). Similarly, Buddha's birthday falls on the 8th day of the 4th month of the .


Judaism


Christianity
  • The spiritual Eighth Day, because the number 7 refers to the days of the week (which repeat themselves).
  • The number of .
  • states that there were eight people on Noah's Ark.
  • The is the eighth king in the Book of Revelation. "Life Application New Testament Commentary", Bruce B. Barton. Tyndale House Publishers, Inc., 2001. , . p. 1257


Islam
  • In , eight is the number of carrying the throne of in heaven.
  • The number of gates of heaven.


Taoism


Other
  • The are Chinese demigods.
  • In , there are eight Sabbats, festivals, seasons, or spokes in the Wheel of the Year.
  • In , it is the number of wealth, abundance. The Goddess has eight forms. There are eight nidhi, or seats of wealth. There are also eight Guardians of the directions.
  • In and Chinese cosmology, the eight trigrams of the . "Bagua" literally means "eight symbols".
  • In Ancient Egyptian mythology, the Ogdoad represents the eight primordial deities of creation.
  • In there are eight dynamics of existence


As a lucky number
  • The number eight is considered to be a lucky number in Chinese and other Asian cultures. Eight (八; accounting 捌; ) is considered a lucky number in Chinese culture because it sounds like the word meaning to generate wealth (發(T) 发(S); : ). Property with the number 8 may be valued greatly by Chinese. For example, a Hong Kong number plate with the number 8 was sold for $640,000. The opening ceremony of the Summer Olympics in Beijing started at 8 seconds and 8 minutes past 8 pm (local time) on 8 August 2008. "Patriot games: China makes its point with greatest show" by Richard Williams, , published 9 August 2008
  • hachi, ya is also considered a lucky number in , but the reason is different from that in Chinese culture. Eight gives an idea of growing prosperous, because the letter () broadens gradually.
  • The Japanese thought of ya as a holy number in the ancient times. The reason is less well-understood, but it is thought that it is related to the fact they used eight to express large numbers vaguely such as Yae Hatae (literally, eightfold and twentyfold), Yakumo (literally, eight clouds), Yaoyorozu no Kami (literally, eight millions of Gods), etc. It is also guessed that the ancient Japanese gave importance to pairs, so some researchers guess twice as yo, which is also guessed to be a holy number in those times because it indicates the world (north, south, east, and west) might be considered a very holy number.
  • In , 8 is the number of building, and in some theories, also the number of destruction.


In astrology
  • In , is the 8th astrological sign of the .
  • In the , 8 was the number of "unmoving" stars in the sky, and symbolized the perfection of incoming planetary energy.


In music and dance
  • A note played for one-eighth the duration of a whole note is called an , or quaver.
  • An , the interval between two with the same letter name (where one has double the frequency of the other), is so called because there are eight notes between the two on a standard major or minor , including the notes themselves and without chromatic deviation. The ecclesiastical are ascending diatonic musical scales of eight notes or tones comprising an octave.
  • There are eight notes in the .
  • Most music is in common (4/4) time, with a primary measure followed by a secondary measure, making a count of eight.
  • There are eight musicians in a double quartet or an octet. Both terms may also refer to a musical composition for eight voices or instruments.
  • Caledonians is a square dance for eight, resembling the .
  • with the number eight in their title include 8 by the Swedish band , 8 by the American rock band Incubus and The Meaning of 8 by Minnesota indie rock band .
  • 's eighth album Octavarium contains many different references to the number 8, including the number of songs and various aspects of the music and cover artwork.
  • "Eight maids a-milking" is the gift on the eighth day of Christmas in the carol "The Twelve Days of Christmas".
  • The 8-track cartridge is a musical recording format.
  • "#8" is the stage name of Slipknot vocalist .
  • "Too Many Eights" is a song by Athens, Georgia's Supercluster.
  • , a Canadian musical group popular in the 1980s with their most notable song "Kiss You (When It's Dangerous)".
  • "Eight Days a Week" is a #1 single for the music group .
  • Figure 8 is the fifth studio album by singer-songwriter , released in the year 2000.
  • Ming Hao from the k-pop group Seventeen goes by the name "The8".


In film and television
  • 8 Guys is a 2003 short film written and directed by .
  • 8 Man (or ): 1963 Japanese manga and anime superhero.
  • 8 Mile is a 2002 film directed by .
  • 8mm is a 1999 film directed by .
  • 8 Women (Original French title: 8 femmes) is a 2002 film directed by François Ozon.
  • is a 2006 film directed by Frank Marshall.
  • Eight Legged Freaks is a 2002 film directed by .
  • Eight Men Out is a 1988 film directed by .
  • , also known as Jennifer 8, is a 1992 film written and directed by .
  • Eight Is Enough is an American television comedy-drama series.
  • In Stargate SG-1 and Stargate Atlantis, dialing an 8-chevron address will open a to another galaxy.
  • The Hateful Eight is a 2015 American western mystery film written and directed by Quentin Tarantino.
  • Kate Plus 8 is an American reality television show.
  • The Weather Channel's segment Local on the 8s features daily and weekly forecasts for regions all over the United States.
  • SBS 8 News is a South Korean primetime news program broadcast on SBS.


In sports and other games
  • is played with a cue ball and 15 numbered balls, the black ball numbered 8 being the middle and most important one, as the winner is the player or side that legally pockets it after first pocketing its numerical group of 7 object balls (for other meanings see Eight ball (disambiguation)).
  • Balklines divide a billiards table into eight outside compartments or divisions called balks. In balkline billiards the table also has eight anchor spaces.
  • In , each side has eight pawns and the board is made of 64 squares arranged in an eight by eight lattice. The eight queens puzzle is a challenge to arrange eight queens on the board so that none can capture any of the others.
  • In the game of eights or , each successive player must play a card either of the same suit or of the same rank as that played by the preceding player, or may play an eight and call for any suit. The object is to get rid of all one's cards first.
  • In association football, the number 8 has historically been the number of the Central Midfielder.
  • in scorekeeping, the is designated as number 8.
  • In , the only position without a proper name is the Number 8, a forward position.
  • In most competitions (though not the European , which uses static squad numbering), one of the two starting props wears the number 8.
  • In rowing, an "eight" refers to a sweep-oar racing boat with a crew of eight rowers plus a .
  • In the 2008 Games of the XXIX Olympiad, the official opening was on 08/08/08 at 8:08:08 p.m. local time in Beijing, China.
  • In the Stanley Parable Demonstration, there is an eight button, that, when pressed, says the word eight.
  • In the racing video game Mario Kart 8, there is an item called the Crazy Eight.


In foods
  • Nestlé sells a brand of chocolates filled with peppermint-flavoured cream called , referring to the time 8 p.m.
  • There are eight vegetables in V8 juice.
  • In cooking recipes, there are approximately 8 pinches to a .


In literature
  • Eights may refer to , usually , lines of verse.
  • The drott-kvaett, an verse, consisted of a stanza of eight regular lines.
  • In 's series, eight is a magical number and is considered taboo. Eight is not safe to be said by wizards on the Discworld and is the number of Bel-Shamharoth. Also, there are eight days in a Disc week and eight colours in a Disc spectrum, the eighth one being .
  • 's poem The Hunting of the Snark has 8 "fits" (cantos), which is noted in the full name "The Hunting of the Snark – An Agony, in Eight Fits
  • Eight apparitions appear to Macbeth in Act 4 scene 1 of Shakespeare's as representations of the eight descendants of .


In slang
  • An "eighth" is a common measurement of marijuana, meaning an eighth of an . It is also a common unit of sale for psilocybin mushrooms. Also, an eighth of an ounce of is commonly referred to as an "8-ball."
  • Referring to the shape of the numeral, eight was formerly represented in bingo slang as "One Fat Lady". Eighty-eight was "Two Fat Ladies".
  • The numeral "8" is sometimes used in informal writing and to represent the syllable "ate", as in writing "H8" for "hate", or "congratul8ions" for "congratulations". 's song "Sk8er Boi" uses this convention in the title.
  • "Section 8" is common U.S. slang for "crazy", based on the U.S. military's Section 8 discharge for personnel.
  • The Housing Choice Voucher Program, operated by the United States Department of Housing and Urban Development, is commonly referred to as the Section 8 program, as this was the original section of the Act which instituted the program.
  • In and , "volverse un ocho" (meaning to tie oneself in a figure 8) refers to getting in trouble or contradicting oneself.
  • In China, "8" is used in chat speak as a term for parting. This is due to the closeness in pronunciation of "8" (bā) and the English word "bye".


See also
  • The Magical Number Seven, Plus or Minus Two


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