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Number Eight

Eight is the natural number following seven and preceding nine, denoted by the symbol 8 or by the word for "eight" in various languages. It is a composite number and the cube of 2 (2³ = 8), making it the smallest perfect cube greater than 1 and the only such cube that is one less than a perfect square (8 = 3² - 1). In mathematics, eight has several notable properties: it is the fourth even number and a power of 2, with prime factorization 2³, and its positive divisors are 1, 2, 4, and 8, summing to 15. It is also a Fibonacci number (the sixth in the sequence) and appears in various geometric contexts, such as the number of vertices in a cube or the sides of an octagon. Beyond basic arithmetic, eight is deficient (its proper divisors sum to less than itself). It also plays a role in group theory as the order of the dihedral group D₄, representing symmetries of the square. Culturally, the number eight holds significant symbolism across traditions. In Chinese culture, it is considered highly auspicious due to its phonetic similarity to the word for "prosperity" or "wealth" (fā), often influencing practices like pricing (e.g., including 8 in amounts for good fortune) and events such as the Beijing Olympics starting at 8:08 p.m. on August 8, 2008. In Tibetan Buddhism, eight represents the Eight Auspicious Symbols (Ashtamangala), embodying enlightenment, victory over ignorance, and spiritual attainment. Historically, eight featured in the "piece of eight," a Spanish silver coin (8 reales) that became a global currency standard from the 16th to 19th centuries, facilitating trade across empires and influencing modern monetary systems.

Etymology and representation

Linguistic origins

The word for the number eight in many derives from the *oḱtṓw, meaning "eight," which is reflected in forms such as oktṓ, Latin octō, eahta, and Proto-Germanic ahtō. This root likely entered these languages through early migrations and cultural exchanges across , with cognates appearing in aṣṭá and ašta. In , the term for eight stems from the Proto-Semitic root *θmn- or *ṯamāniy-, denoting "eight," as seen in Arabic θamāniyah (eight) and Hebrew šəmōnāh (eight), with the root emphasizing the numeral in compounds like Akkadian samānu. This root is distinct from Indo-European derivations and highlights independent developments in Afro-Asiatic numeral systems, where the form often exhibits gender polarity in agreement with nouns. The word for eight, 八 (bā), originates from *prēt or *priāt-, reconstructed within the Sino-Tibetan , unrelated to Indo-European or roots but sharing distant ties to forms like brgyad. In , hachi derives from the Sino-Japanese on'yomi reading of the same character 八, borrowed via Chinese script during historical linguistic contact.

Evolution of the digit

The digit 8 originated in the Brahmi numeral system of ancient , dating back to the BCE, where it was typically depicted as two small circles stacked one above the other or as a single continuous curve resembling a vertical figure-eight precursor. This representation evolved during the (4th to 6th centuries CE), transitioning into a more angular shape akin to a right-angled hook or └┐ form, reflecting adaptations for inscription on materials like palm leaves and influenced by the empire's territorial expansion. By the 8th and 9th centuries , these Indian numerals were transmitted to the through scholarly exchanges, where they were refined in the Perso-Arabic tradition. In eastern variants, the digit 8 adopted a simple wedge-like (٨), while some manuscripts featured a 5-like form with a curved line and small loop; these changes arose from scribal practices and the needs of on dust boards (ghubar). In the western Islamic regions, particularly (Islamic Spain) by the , the numeral standardized into a more recognizable looped structure, with two enclosed circles connected by a vertical stem, as seen in works by mathematicians like al-Banna al-Marrakushi in the . The modern Western form of 8 emerged through European adoption via trade and translation efforts in , culminating in its widespread use by the 13th century as described in Fibonacci's (1202). Regional variations persist today, with the Eastern ٨ retaining a sharper, open wedge compared to the closed loops of the Western 8. The digit's shape bears no direct historical relation to the (∞), which introduced in 1655, possibly inspired by the Greek letter omega (ω) or the Roman numeral for 1,000 (CIƆ). Johannes Gutenberg's development of movable-type printing in the 1450s accelerated the standardization and dissemination of across Europe, fixing the looped 8 in printed texts and facilitating its global dominance.

Mathematics

Arithmetic properties

Eight is a , specifically the sixth number in the , and it is an even composite integer with the prime factorization $2^3. Its positive divisors are 1, 2, 4, and 8. The sum of these divisors is 15, while the sum of the proper divisors (excluding 8 itself) is 7, which is less than 8, making it a . Furthermore, this deficiency of exactly 1 classifies 8 as an number, a property shared by all known powers of 2. It is also a perfect as $2^3, and notably the only nonzero perfect power differing by 1 from , since $3^2 - 1 = 8. Basic arithmetic operations with 8 include , such as $8 + 8 = [16](/page/16), and its and facts, which are determined by its divisors. The for 8 up to 12 is:
MultiplierProduct
18
2
3
4
540
6
756
8
9
10
11
1296
Division of 8 by its divisors yields integers: $8 \div [1](/page/1) = 8, $8 \div 2 = 4, $8 \div 4 = 2, and $8 \div 8 = [1](/page/1). Powers of 8 include $8^[1](/page/1) = 8, $8^2 = [64](/page/64), and $8^3 = 512. The principal of 8 is \sqrt{8} = 2\sqrt{2} \approx 2.828. Its is exactly 2, since $2^3 = 8. In , 8 is represented as $1000_2, equivalent to $1 \times 2^3 + 0 \times 2^2 + 0 \times 2^1 + 0 \times 2^0. In , it is $8_{16}.

Geometric significance

In geometry, the number eight is prominently featured in the regular octagon, a with eight equal sides and s. Each interior of a regular octagon measures 135 degrees, derived from the general formula for the interior of a regular n-gon: \frac{(n-2) \times 180^\circ}{n}, where n = 8. The area of a regular octagon with side length s is given by $2(1 + \sqrt{2})s^2, which reflects its composition of a square with isosceles right triangles attached to each side. This shape exhibits eight-fold and is commonly used in architectural designs for its balance of perimeter efficiency and enclosed space. Extending to three dimensions, the regular is a with eight equilateral triangular faces, six vertices, and twelve s. It serves as the to the , where the vertices of the octahedron correspond to the faces of the cube, and vice versa; for a regular octahedron with edge length a, its dual cube has edge length \frac{a}{\sqrt{2}}. The volume of a regular octahedron is \frac{\sqrt{2}}{3} a^3, highlighting its compact spatial configuration. Archimedean solids and s further incorporate eight in configurations with eight-fold . For instance, the , an , features eight equilateral triangular faces and six regular octagonal faces, resulting from truncating the vertices of a while preserving edge uniformity. In planar , the truncated square (Schläfli symbol t{4,4} or 4.8.8) is a semiregular Archimedean composed of regular octagons and squares, where each is surrounded by one square and two octagons, exhibiting local eight-fold aligned with the octagonal elements. These structures demonstrate eight's role in uniform polyhedral and designs that maximize and packing density. In higher dimensions, eight manifests in the (or octeract), a regular hypercube with 256 vertices, 1024 edges, 1792 square faces, and 1792 cubic cells, generalizing the to eight-dimensional . Projections of the onto lower dimensions, such as , reveal intricate wireframe skeletons that aid in visualizing high-dimensional geometry, often used in computational modeling. Similarly, the eight-point represents a geometric division of the plane into eight 45-degree sectors, originating from and intercardinal directions (north, northeast, east, etc.), providing a foundational for and angular measurement with eight-fold rotational invariance. Recent applications leverage octagonal structures in 3D printing for enhanced efficiency. In 2024 studies on bioinspired metamaterials, octagonal designs in thin-walled composite tubes demonstrated superior energy absorption under axial loading compared to hexagonal or square , optimizing use and structural in additive manufacturing.

Advanced mathematical structures

The form an 8-dimensional normed over the real numbers, extending the quaternions through the Cayley-Dickson construction and representing the highest-dimensional such algebra. Unlike quaternions, octonion multiplication is non-associative, though it remains and satisfies the division property that every non-zero element has an inverse. This structure is power-associative and normed, with the norm defined by the norm on the underlying , preserving the multiplicative property ||xy|| = ||x|| ||y||. are linked to the exceptional Lie group E₈ through their , which is G₂, and more broadly influence the classification of division algebras via Hurwitz's , limiting real normed division algebras to dimensions 1, 2, 4, and 8. In group theory, 8 is the order of the smallest non-abelian groups, with two isomorphism classes: the dihedral group D₄ (symmetries of the square) and the quaternion group Q₈. D₄ has presentation ⟨r, s | r⁴ = s² = 1, s r s⁻¹ = r⁻¹⟩ and contains five conjugacy classes, while Q₈ = {±1, ±i, ±j, ±k} with i² = j² = k² = i j k = -1 exhibits a cyclic center of order 2. These groups illustrate the transition from abelian to non-abelian structures at order 8, as all groups of order less than 8 are abelian. The exceptional Lie group E₈, of rank 8 and dimension 248, possesses a root system with 240 roots in an 8-dimensional Euclidean space, making it the largest simple Lie group of exceptional type. Its Weyl group has order 2¹⁴ × 3⁵ × 5 × 7, and E₈ is simply laced with all roots of equal length. Clifford algebras exhibit a periodicity of 8 in their structure over the real numbers, meaning that the algebra Cl_{n+8} is periodically related to Cl_n via tensor products with matrix algebras and the octonions. Specifically, the real Clifford algebra Cl_8 ≅ M_{16}(ℝ), where M_k(ℝ) denotes the algebra of k×k real matrices, and this 8-fold periodicity arises from the Bott periodicity theorem in K-theory. In dimension 8, spinors correspond to irreducible representations of the spin group Spin(8), which has dimension 28 and three 8-dimensional half-spin representations, reflecting the triality automorphism of Spin(8). This periodicity underpins the classification of Clifford modules and their role in representing orthogonal transformations in even dimensions. In number theory, the quadratic residues modulo 8 are 0, 1, and 4, as squares of integers modulo 8 yield only these values: even numbers square to 0 or 4, while odd numbers square to 1. This follows from enumerating residues: 0² ≡ 0, 1² ≡ 1, 2² ≡ 4, 3² ≡ 1, 4² ≡ 0, 5² ≡ 1, 6² ≡ 4, 7² ≡ 1 (mod 8). Euler's theorem extends Fermat's little theorem to composite moduli like 8, stating that if gcd(a, 8) = 1, then a^{φ(8)} ≡ 1 (mod 8), where φ(8) = 4, so a⁴ ≡ 1 (mod 8) for odd a. This holds because the multiplicative group (ℤ/8ℤ)^* is isomorphic to C₂ × C₂, of order 4, confirming the exponent divides 4. In 2025, researchers at , Mikko Partanen and Jukka Tulkki, proposed a of using an eight-spinor based on four one-dimensional unitary U(1) gauge symmetries. This framework, termed unified gravity, derives four-dimensional space-time quantities dynamically from an eight-dimensional spinor structure via a space-time dimension field, unifying gravitational and gauge interactions in a manner compatible with symmetries and the teleparallel equivalent of . The theory demonstrates renormalizability at one-loop order, advancing toward a complete formulation.

Science and nature

In physics

In , the number 8 is recognized as one of in the , which describes the arrangement of protons and neutrons in nuclei analogous to shells in atoms. These correspond to particularly stable configurations where nuclear shells are completely filled, leading to enhanced and resistance to decay. Specifically, 8 protons or 8 neutrons fill the first three subshells (1s_{1/2}, 1p_{3/2}, 1p_{1/2}), resulting in exceptional stability; a prominent example is the nucleus, which has 8 protons and 8 neutrons, making it doubly magic and one of the most stable light nuclei. In (QCD), the theory governing the , the number 8 manifests in the structure of gluons, the force-carrying bosons that mediate interactions between quarks via . QCD is based on the SU(3) gauge group, which has 8 generators, corresponding to 8 distinct gluons forming a color octet; these gluons carry both color and anticolor, enabling self-interactions that contribute to phenomena like confinement. This octet structure arises from the non-Abelian nature of SU(3), distinguishing QCD from . The eightfold way, proposed by in 1961, organizes hadrons—particles like protons and mesons bound by the strong force—into multiplets under approximate SU(3) flavor , with octets playing a central role. In this classification, the baryon octet includes the proton (uud quarks), (udd), and six hyperons, all with and sharing similar masses due to the ; this scheme predicted the existence of the Ω⁻ baryon (sss), later discovered experimentally. The framework laid the groundwork for the , revealing hadrons as composites of up, down, and strange quarks. In theoretical frameworks beyond the Standard Model, such as superstring theory, the number 8 appears in the dimensional structure of heterotic strings, which unify bosonic and superstring sectors in 10 spacetime dimensions. The E₈ × E₈ heterotic string theory embeds the Standard Model gauge groups using two copies of the 8-dimensional E₈ root lattice to construct the internal fermionic degrees of freedom, ensuring anomaly cancellation and providing a grand unified structure; this lattice realization facilitates compactifications to four dimensions while preserving supersymmetry. Hypothetical spin-8 particles, representing higher-spin excitations, arise in such string-inspired extensions, where infinite towers of massive states include spins up to and beyond 8, potentially observable as Kaluza-Klein modes.

In chemistry

In chemistry, the number eight is fundamentally significant through the , which describes the tendency of atoms to achieve stability by attaining eight valence electrons in their outermost shell, mimicking the of . This principle governs much of chemical bonding and reactivity in main-group elements, as seen in the periodic table where elements in periods 2 and 3 commonly form compounds to satisfy this configuration. For instance, atoms like carbon and oxygen share or transfer electrons to reach an octet, promoting stable molecular structures. However, exceptions exist, such as , which follows a duet rule by achieving two valence electrons for stability, and elements like that can form bonds with fewer than eight electrons in certain compounds. Oxygen, with 8, exemplifies the as a key in the chalcogen group of the periodic table. It has six valence electrons and readily forms the O₂ through a double , allowing each oxygen atom to achieve eight electrons in its valence shell. This configuration underpins oxygen's high reactivity, enabling its essential roles in biological respiration—where it acts as the final in cellular processes—and in oxidation reactions critical for and . Oxygen's abundance and bonding behavior make it indispensable in both natural and industrial chemical contexts. Beyond simple molecular bonding, eight manifests in coordination chemistry through octacoordinate complexes, where a central metal atom or is surrounded by eight ligands, often adopting geometries like or for stability. A classic example is the octacyanomolybdate(IV) , [Mo(CN)₈]⁴⁻, in which the molybdenum center coordinates eight ligands, exhibiting dodecahedral in solution and demonstrating how higher coordination numbers extend octet-like principles to transition metals. These structures highlight eight's role in facilitating complex architectures with potential applications in and . Recent advancements in have drawn inspiration from the to design innovative catalysts. In 2025, researchers developed carbon-like nanomaterials using an octet-rule-derived ONa₆ supercarbon building block, forming octahedral clusters that enable bandgap engineering in perovskites for enhanced photocatalytic efficiency. This approach leverages the stability of octet configurations at the nanoscale to create metal-free catalysts with improved performance in energy conversion processes.

In biology

In the class Arachnida, which includes spiders and scorpions, all members possess eight legs as a defining characteristic, adapted for locomotion, predation, and environmental navigation in terrestrial and some subterranean habitats. This eight-legged configuration provides enhanced stability and maneuverability, particularly in uneven terrains, as evidenced by evolutionary diversification patterns in arachnids that emphasize robust structures for survival. Spiders, for instance, utilize these legs for web construction, sensing vibrations, and rapid escape responses, contributing to their success across diverse ecosystems. The octopus, belonging to the phylum and class , features eight flexible arms equipped with suckers, enabling precise manipulation of objects, prey capture, and locomotion through or crawling. These arms are integral to the octopus's renowned , demonstrated by problem-solving behaviors such as use and in settings. Additionally, octopuses exhibit advanced capabilities via specialized skin cells called chromatophores, allowing rapid color and texture changes to evade predators or ambush prey in coral reefs and open oceans. In , the comprises 64 possible three-base codons that specify 20 and stop signals, with degenerate subsets where multiple codons encode the same to buffer against mutations. For example, nine —phenylalanine, , , , , , , , and —are each assigned to exactly two codons, forming compact subsets that enhance coding efficiency. (tRNA) molecules, which translate these codons, feature anticodon loops typically consisting of seven to nine nucleotides, with certain configurations modeled as eight-nucleotide loops to optimize codon-anticodon pairing and decoding accuracy during protein synthesis. Human anatomy reflects the number eight in several skeletal and neural structures essential for mobility and sensation. The region of the gives rise to eight pairs of (C1 through C8), which emerge from the to innervate the , shoulders, and upper limbs, facilitating and sensory feedback despite there being only seven . In the , eight —arranged in proximal (scaphoid, lunate, triquetrum, pisiform) and distal (, , capitate, hamate) rows—form a flexible yet stable joint that articulates with the , , and metacarpals, enabling hand dexterity and load distribution.

Technology

Computing and information theory

In computing, the byte serves as the fundamental unit of digital information storage and transmission, standardized as a sequence of eight bits. This definition was formalized by the in ISO/IEC 2382-1:1993, which established the byte as consisting of eight bits to provide a consistent measure for data quantities across systems. The adoption of eight bits per byte originated from early computing hardware designs, such as IBM's /360 in the 1960s, where it balanced efficiency in character encoding and processing power, allowing representation of 256 distinct values (2^8). The American Standard Code for Information Interchange (ASCII), initially defined as a seven-bit encoding scheme by ANSI X3.4-1968, supported 128 characters including control codes and printable symbols, with the eighth bit often reserved for parity checks in early serial communications to detect transmission errors. As hardware evolved to eight-bit architectures, variants emerged, utilizing the full eight bits to encode up to 256 characters; the ISO 8859 series, introduced in 1987, standardized these extensions for international use, enabling support for accented letters and symbols in Latin-based languages. In networking protocols, particularly those in the , the term "octet" denotes an eight-bit byte to avoid ambiguity with varying byte sizes in older systems, ensuring across diverse hardware. IPv4 addresses, defined in RFC 791 (1981), consist of 32 bits divided into four octets, each ranging from 0 to 255 and typically represented in dotted decimal notation (e.g., 192.168.1.1), which delineates and portions for . protocols further employ octets as the basic unit for packet headers, calculations, and data segmentation, with the octet stream facilitating reliable byte-oriented transmission in segments. The number eight's alignment with powers of two—specifically 8 = 2^3—underpins binary-based memory addressing and data in modern architectures. In 64-bit systems, such as those using the instruction set, memory addresses and registers operate on 64-bit words, equivalent to eight bytes, enabling efficient access to large address spaces up to 2^64 bytes while maintaining for optimal in operations like pointer arithmetic and cache line fetches. Error-correcting codes in computing often leverage eight-bit blocks for single-error correction and double-error detection (SECDED). The extended Hamming code, an evolution of the original (7,4) code proposed by Richard Hamming in 1950, adds an overall parity bit to form an (8,4) configuration that corrects one-bit errors in four data bits; for eight data bits, a (12,8) variant incorporates four parity bits to protect against single-bit flips in memory or transmission, widely implemented in DRAM error correction since the 1970s. In , groupings of eight qubits have emerged as compact units for error-resistant algorithms, addressing noise in physical qubits. In 2025, demonstrated a using exactly eight qubits in a compact error-detecting code to prepare two logical states, enabling repeated operations below the and advancing fault-tolerant computation with reduced overhead compared to larger codes like surface codes.

Engineering and measurements

In engineering and measurements, the number eight frequently appears in standardized units and practical applications, reflecting historical conventions and design efficiencies that balance functionality with manufacturability. For instance, in the customary system, a is defined as 8 fluid ounces, serving as a fundamental volume measure in , , and industrial to ensure consistency across recipes and scales. Similarly, in , 8 mm establishes the standard for and formats, where the film's width allows for compact spools while capturing sufficient image area for projection, as pioneered in early 20th-century motion picture technology. In , the V8 configuration denotes an with eight cylinders arranged in two banks forming a V shape, optimizing power delivery and balance for high-performance vehicles like trucks and sports cars, a design that has been widely adopted since the early 1900s for its smooth operation and torque output. Complementing this, 8-speed automatic transmissions have become prevalent in modern automobiles, enabling finer gear ratios for improved and ; for example, the ZF 8HP series integrates eight forward gears in a compact planetary gearset, reducing engine load across a broad speed range and enhancing overall vehicle economy. Architectural standards also incorporate eight in modular and material specifications to streamline construction. Eight-story buildings are common in modular designs, where prefabricated units stack efficiently to meet urban density needs while minimizing on-site assembly time, as demonstrated in projects like the 5th Street Modular Housing in , which uses modules for rapid erection of . Additionally, 8-foot lengths represent a standard dimension for dimensional lumber, such as 2x4 studs, facilitating compatibility with common wall heights and reducing waste in framing for residential and light commercial structures. Labor engineering standards trace the 8-hour workday to 19th-century movements, where the in 1866 issued the first national call for limiting shifts to eight hours to combat industrial overwork, influencing subsequent legislation like the Adamson Act of 1916 that mandated it for railroad workers. In contemporary electric vehicle design, 8-module configurations enhance efficiency by arranging pouch or prismatic cells into scalable series-parallel setups; the 2024 , for instance, employs an 8S3P (eight cells in series, three parallel) configuration within its battery modules, achieving a balance of voltage, capacity, and thermal management for extended range.

Culture and symbolism

Religious and spiritual meanings

In , the number eight holds profound symbolic significance, particularly through the Dharmacakra, or Wheel of Dharma, which features eight spokes representing the —comprising right view, right intention, right speech, right action, right livelihood, right effort, right , and right concentration—as the core teachings for attaining . Additionally, the Eight Auspicious Symbols, known as , include the parasol (protection from ), pair of golden (fearlessness in samsara), vase (inexhaustible merit), lotus (purity), right-turning conch shell (Dharma's proclamation), (interdependence), victory banner (triumph over obstacles), and Dharmacakra itself, collectively embodying the gifts offered to at his and invoking good fortune in and broader Buddhist traditions. In , eight manifests in the Ashtalakshmi, the eight manifestations of the goddess , each governing a facet of prosperity: Adi Lakshmi (primeval wealth), Dhana Lakshmi (monetary fortune), Dhanya Lakshmi (agricultural abundance), Gaja Lakshmi (power and royalty), Santana Lakshmi (progeny and family), Veera Lakshmi (courage), Vijaya Lakshmi (victory), and Vidya Lakshmi (knowledge), worshipped to invoke holistic well-being and balance in devotees' lives. The tradition also recognizes eight directions (ashtadik) in , an ancient architectural science, guarded by the Ashtadikpalakas—deities such as (east), (southeast), (south), Nirriti (southwest), (west), (northwest), (north), and (northeast)—who ensure cosmic harmony and protect structures aligned with these orientations for positive energy flow. Judaism attributes spiritual depth to eight as a marker of transcendence beyond the natural order of seven, exemplified by the eight nights of , commemorating the miracle of oil lasting in the rededicated , symbolizing and the infusion of light into the world. This theme echoes in the brit milah ritual, where circumcision occurs on the eighth day of a male child's life, signifying entry into the with and a new spiritual beginning that elevates the individual above mere physical existence. In , eight symbolizes and renewal, tied to the "eighth day" as the first day of the new creation following the seven-day account, with ' occurring on this day, heralding eternal life. The practice of on the eighth day, rooted in law ( 17:12), prefigures spiritual circumcision of the heart through faith in Christ, as elaborated in teachings (Colossians 2:11). The Eight in :3-10 further reinforce this, outlining blessings for the meek, merciful, pure in heart, and persecuted, forming the ethical foundation of the and promising divine favor in the kingdom of heaven. Within , the octagram known as serves as a sacred geometric symbol in Quranic manuscripts and architecture, dividing the text into 60 hizbs (sections) and representing harmony and the structured revelation of divine guidance. Interpretations of Paradise () describe it as having eight gates, each named for virtues like prayer (Bab al-Salah), fasting (Bab al-Rayyan), and charity (Bab al-Sadaqah), as referenced in hadith collections, symbolizing the multifaceted paths to divine reward and mercy for the righteous.

Superstitions and numerology

In , the number eight is widely regarded as the luckiest digit due to its pronunciation "bā," which phonetically resembles "fā," meaning to prosper or generate wealth. This association has led to a strong preference for incorporating eight into phone numbers, addresses, and license plates, often commanding premium prices in auctions or registrations. Similarly, in Japanese tradition, eight holds auspicious significance because its kanji character (八) visually widens toward the base, symbolizing expansion, growth, and prosperity—a concept known as suehirogari. However, the looping shape of eight, resembling the when rotated, has inspired rare superstitions associating it with an unending cycle that can evoke unease or fear, as seen in , a specific aversion to the number triggered by its figure-eight form. In Western folk beliefs, eight carries a connotation of misfortune through the "behind the ," originating from the game of where the black eight ball obstructs a player's shot, leaving them in a disadvantaged or precarious position. In , particularly within traditions tracing back to Pythagorean influences, eight embodies balance between the material and spiritual realms, representing karma through its that signifies eternal cycles of cause and effect, as well as themes of and . This duality underscores eight's role as a number of and , where personal efforts yield tangible rewards while maintaining cosmic harmony. Astrologically, the eighth house governs profound , intimacy, shared resources, and rebirth, often linked to life's mysteries such as and psychological evolution, ruled by and . In medieval interpretations, eight symbolized perfection and the perpetual order of the , with its form evoking the progression beyond the seven classical .

In arts, literature, and media

In music, the represents a fundamental spanning eight notes in the , from a starting to the with double its , creating a sense of resolution and completeness. Composers often structure phrases in eight-bar units to establish rhythmic balance and formal coherence, as these segments align with natural cadential patterns in Western tonal music. In literature, the number eight holds symbolic weight in Terry Pratchett's series, where it signifies magic, exemplified by the eighth color of the rainbow, octarine, visible only to wizards due to the octagonal structure of their eyes. Similarly, in Dante Alighieri's , the eighth circle of Hell, known as , punishes sins of fraud through ten concentric ditches, emphasizing deception's layered complexities. Eight-fold symmetry features prominently in visual arts, particularly in Islamic geometric tile designs, where rosettes and patterns constructed around an octagonal framework create intricate, repeating motifs that evoke infinity and harmony. Mandalas often incorporate this symmetry, dividing circular forms into eight equal sections to symbolize and wholeness in meditative art traditions. explored figure-eight forms in works like Möbius Strip II (1963), depicting ants traversing a twisted band that loops endlessly, blending mathematical with illusory depth. In media, the number eight appears in film titles such as (2018), a featuring an all-female ensemble led by Debbie Ocean, who assembles seven accomplices for a high-stakes robbery. Classic arcade video games frequently structure progression around eight levels, as seen in Super Mario Bros. (1985), where players navigate eight worlds culminating in a climactic confrontation.

In sports, games, and recreation

In various sports, the number eight plays a structural role in team compositions, equipment, and event formats. In co-recreational Ultimate Frisbee, teams consist of eight players, typically four men and four women, to promote balanced mixed-gender play on the field. Eight-ball, a popular variant of pool billiards, involves two players or teams pocketing seven object balls each from assigned groups (solids 1-7 or stripes 9-15) before legally pocketing the black eight ball to win; pocketing the eight ball prematurely or on a foul results in loss of game. Figure-eight racing, a motorsport discipline, utilizes tracks shaped like the numeral eight, where vehicles cross paths at the center intersection, demanding precise timing to avoid collisions during oval-style laps. In the Olympics, eight features prominently in certain events, such as the men's eight in , where a crew of eight rowers plus a competes in a single boat over 2,000 meters. finals, like the 100-meter dash, accommodate eight competitors across standard lanes to determine . In games, chess begins with each player deploying eight pawns across the second rank (for white) or seventh rank (for black), forming the frontline in strategic positioning. Role-playing games like employ the eight-sided die (d8), an octahedral numbered 1-8, for resolving outcomes such as weapon damage or hit points for classes like clerics. Recreational activities often incorporate eight in measurable challenges, including 8-kilometer runs, which serve as accessible distances for community events blending with social participation, as seen in races like the 8K. formats, such as 8-hour events, divide team efforts into timed segments for multisport disciplines like trekking and , emphasizing endurance over a fixed duration. In esports, 2024 tournaments frequently used 8-team brackets for knockout stages; for instance, the Esports World Cup featured an 8-team single-elimination playoff to crown the champion.

Idioms, slang, and other uses

Everyday language and expressions

In everyday language, the number eight frequently appears in terms related to measurements and informal quantities. In , an "eighth" refers to one-eighth of an (approximately 3.5 grams) of marijuana, a common purchase size for personal use. Similarly, "" or "8-ball" is for one-eighth of an (approximately 3.5 grams) of or other drugs such as . This term stems directly from the fractional measurement and is widely used in dispensaries and among consumers. The "behind the eight ball" describes a situation where someone is at a disadvantage or in a difficult position, originating from the game of (also known as pocket billiards). In , the eight ball is the black ball that must be pocketed last; being positioned such that the cue ball is blocked by it creates an unfavorable shot, leading to the metaphorical sense of being trapped or unlucky. The phrase first appeared in in the 1920s and remains a staple in casual conversation for expressing setbacks. Historical idioms tied to currency also incorporate eight, notably "," which denoted the silver valued at eight reales. Minted from the onward, this —often simply called the ""—circulated widely in global trade, including in the and , due to its high silver content and standardized weight of about 27 grams. Its name derived from the eight reales it represented, and it influenced , with "" entering English vernacular as a symbol of pirate treasure and colonial wealth. In Spanish-speaking contexts, particularly in and , the "volverse un ocho" (to turn into an eight) means to become confused, overly complicated, or entangled in trouble, evoking the image of twisting into a . This expression is used colloquially to describe situations or people getting messily involved or self-contradictory. and texting often replaces sounds with numbers resembling them, including eight for phonetic purposes. In internet and mobile messaging, "88" stands for "bye bye" because its (bā bā) mimics "bài bài," a casual farewell borrowed from English. Similarly, in English leetspeak (or "1337 speak"), a and gamer dialect from the 1980s onward, the 8 substitutes for the "ate" sound, as in "gr8" for "great" or "l8" for "late," due to visual and phonetic similarity.

Miscellaneous applications

In historical contexts, the number eight marks significant milestones, such as the CE, when , King of the , expanded his realm into a vast across much of Western and , culminating in his coronation as Emperor of the Romans by on December 25, 800. This event symbolized the revival of imperial authority in the West after the fall of Rome and influenced the development of medieval European governance. Additionally, in the United States, the 22nd Amendment to the Constitution, ratified in 1951, limits presidents to two elected terms, effectively capping service at eight years to prevent indefinite tenure, a response to Franklin D. Roosevelt's four-term presidency. Ancient timekeeping systems incorporated eight-day cycles, notably in the calendar's , an eight-day period ending with a day that structured , , and public assemblies from the era through the early Empire. In , eight percent has appeared as a historical benchmark for interest rates during periods of moderate . Daily health guidelines frequently reference eight, including the common advice to consume eight glasses (approximately 64 ounces or 2 liters) of per day for adequate , though emphasizes individualized needs based on factors like activity and climate rather than a fixed quota. Similarly, eight hours of per night is widely recommended for adults to support cognitive function, immune , and overall well-being, aligning with expert ranges of seven to nine hours. In transportation, eight-passenger vehicles like minivans and SUVs, such as the and , provide seating for larger families or groups, offering versatile options for road travel with features like removable seats and ample cargo space. Highways designated as Route 8 exist across various U.S. states, including , which spans 280 miles primarily through , connecting rural areas to urban centers like La Crosse and serving as a key east-west corridor since its establishment in the .