Mathematics

Cryptosystem: definitions, structure, history and uses Cryptosystem An overview of cryptosystems: meanings, components (key generation, encryption, decryption), historical development, types (symmetric/asymmetric), uses, and key security distinctio…

Cube (geometry) Cube A cube is a regular hexahedron with six square faces and equal edge lengths; this article explains its properties, formulas, history, and common uses.

Cubic centimetre (cm³, cc): definition, conversions and common uses Cubic centimetre A cubic centimetre (cm³ or cc) is the volume of a 1 cm × 1 cm × 1 cm cube. It equals 1 millilitre (1 mL) and is widely used in medicine and engine displacement.

Cubic foot (ft³): definition, conversions, uses, and distinctions Cubic foot A cubic foot (ft³) is the volume of a cube one foot on a side. This article explains its definition, common conversions, practical uses, and how it compares to related units.

Cubic inch (in³): definition, conversions, history and common uses Cubic inch The cubic inch is a unit of volume in the Imperial and US customary systems. This article explains its definition, conversions to metric units, historical context, typical uses (no…

Cubic metre (m³) — SI unit of volume Cubic metre The cubic metre (m³) is the SI derived unit for volume, defined by a cube one metre on each side. Commonly equal to 1,000 litres and about 1,000 kilograms of water under typical co…

Cubit — ancient unit of length based on the forearm Cubit Cubit: an ancient, anthropometric unit of length based on the forearm. Overview of its definitions, regional variants, historical use, surviving standards and its role in construct…

Cuboid: definition, geometry, formulas, and applications Cuboid A cuboid is a six-faced polyhedron whose faces are quadrilaterals; rectangular cuboids (right rectangular prisms) and the cube are important special cases with widely used volume a…

Curl (vector operator) Curl The curl is a vector operator that measures the local rotational tendency of a vector field in three-dimensional space. It appears in physics, engineering and differential geometry…

Currying: Transforming Multi-argument Functions into Unary Chains Currying Currying rewrites a function that takes multiple arguments into a sequence of single-argument functions. It is fundamental to lambda calculus and functional programming and enables…

Curve: definitions, types, equations, history and uses Curve A curve is a continuous path or locus of points in a plane or space. This article explains intuitive and mathematical definitions, common forms and equations, historical developmen…

Curve fitting: methods, uses, and practical considerations Curve fitting An accessible overview of curve fitting: fitting functions to data through interpolation or smoothing, common algorithms and models, historical background, applications, and cautio…

Cyclic redundancy check (CRC): polynomial checksum for error detection Cyclic redundancy check CRC is a polynomial-based checksum used to detect accidental data corruption in networks, storage and file formats. Explains how CRCs work, common variants, implementation techniqu…

Cylinder (geometry) Cylinder A cylinder is a three-dimensional shape generated by parallel lines around an axis; includes definitions, common formulas for volume and surface area, variants (circular, elliptic,…

Cyrillic numerals A historic numeral system that used Cyrillic letters to represent numbers, developed for Old Church Slavonic texts and later used across Slavic manuscripts and inscriptions before…

D (the letter) D Comprehensive overview of the letter D: origin, shapes, pronunciation, typographic variants, uses in language, science, music, numeration and common symbolic roles.

Data Facts or values recorded in a form suitable for analysis, reference, or processing; includes numbers, text, images, audio and metadata, and underlies statistics, computing and deci…

David Hilbert German mathematician David Hilbert (1862–1943) made foundational contributions to algebra, analysis, geometry, logic and the formal foundations of mathematics, and shaped 20th‑cent…

De Moivre's formula: statement, forms, history and applications De Moivre's formula A clear account of de Moivre's formula relating complex numbers and trigonometry: statement in trigonometric and polar forms, proofs, historical origin, uses (powers, roots, roots…

Decade: Definition, Counting Methods, History and Cultural Uses Decade A decade is any span of ten years. This article explains definitions, counting conventions, origin of the term, cultural labels (the 1920s, the eighties), and common usages in age,…

Decagon (ten-sided polygon) Decagon A decagon is a ten-sided polygon. This article explains its geometry, key measurements, symmetry, construction, variants such as star decagrams, and common uses and distinctions.

Decasecond (10 seconds) Decasecond A decasecond is an SI-derived unit equal to ten seconds (10 s). It is occasionally used to express short durations in science, media, and everyday timing.

Decibel (dB): definition, calculation, and common uses Decibel The decibel (dB) is a logarithmic unit that expresses ratios of power or amplitude. Used across acoustics, electronics and telecommunications, it simplifies multiplication of gains…

Decidability theory: computability, undecidability and semi-decidable problems Decidability theory Overview of decidability theory in mathematical logic and computer science: definitions, examples, history, significance, and distinctions including decidable, undecidable and semi…

Decimal (base ten) numeral system Decimal Overview of the decimal (base ten) system: its structure, history, decimal fractions and separators, common uses, and distinctions from other numeral systems.

Decimal separator: point, comma, and other radix marks Decimal separator Symbol that separates the integer and fractional parts of a decimal numeral (commonly a point or comma), its variants, history, examples, and practical implications for writing and…

Decision problem (yes–no questions in computation) Decision problem A decision problem asks a yes-or-no question about an input in a formal system. Central to computability and complexity, it distinguishes decidable, undecidable and hard problems a…

Decision theory: principles, branches, and applications Decision theory Decision theory studies how agents choose between alternatives under uncertainty, combining probability, statistics, logic, and models to evaluate consequences and guide rational o…

Deduction: logic, reasoning, natural deduction, and tax deductions Deduction Deduction refers to drawing conclusions from premises (formal logic and everyday reasoning) and to amounts subtracted from income for tax or accounting; covers types, history, exam…

Deductive reasoning Deductive reasoning: definition, structure, main forms, historical development, examples, uses, and how it differs from induction and other reasoning types.

Degree (angle measurement) Degree (angle) A degree is a unit for measuring plane angles: 360° equals a full circle. This article explains definition, subdivisions, relation to radians, history, applications, and notable di…

Degree of a Polynomial (mathematics) Degree (mathematics) The degree of a polynomial is the largest exponent with a nonzero coefficient. This article explains definitions, notation, properties, multivariable variants, examples, and common…

Delta (Greek letter Δ / δ): forms, history, and common uses Delta Overview of the Greek letter delta (Δ, δ): its phonetic value, numeric role, historical descendants, mathematical and scientific meanings, and the river-delta name connection.

Denominator (mathematics) Denominator In a fraction, the denominator is the quantity below the division line that indicates the number of equal parts; it cannot be zero and plays a central role in arithmetic and algebr…

Derivative (mathematics): definition, notation, rules, and applications Derivative (mathematics) A derivative measures a function's instantaneous rate of change. Covers definitions, notation (dy/dx, f′), basic rules, history, examples, and why differentiability matters in scie…

Descriptive statistics: summarizing and visualizing data Descriptive statistics Concise guide to descriptive statistics: purpose, common measures (mean, median, variance), graphical displays, data types, robust measures, applications and limitations.

Determinant (linear algebra concept) Determinant A determinant is a scalar value associated with a square matrix that encodes invertibility, volume scaling, orientation, and many algebraic properties. This article explains defini…

Deterministic algorithm: definition, properties, examples and contrasts Deterministic algorithm A deterministic algorithm always produces the same output for a given input and follows a predictable sequence of steps. Overview, characteristics, common examples, uses, and contr…

Diagonal: definition, properties, counting and applications Diagonal A diagonal is a line segment joining nonadjacent vertices of a polygon or entries along a matrix's main line. Article covers geometric definition, formulas, properties, other meani…

Diameter (geometry and metric concept) Diameter The diameter is a line segment through the center of a circle or sphere and its length; more generally it is the largest distance between points in a set. Key formulas, symbols, an…

Dice: forms, history, uses, and notable properties Dice Overview of dice: common shapes, numbering, history, uses in games and gambling, fairness issues, polyhedral varieties, and practical notes for play and manufacture.

Dictionary attack A dictionary attack is a password-cracking method that tests likely words and phrases from curated lists. It contrasts with brute-force attacks and can be mitigated by salting, com…

Difference An overview of the concept of difference: meanings in mathematics, language, philosophy and everyday use, with examples, history, and common distinctions from related terms.

Difference Quotient (average rate of change and approach to the derivative) Difference quotient The difference quotient computes a function's average rate of change between two points. It is the core expression whose limiting form gives the derivative and is used in algebra,…

Differential: meanings in mathematics, mechanics and medicine Differential Overview of 'differential' as a mathematical concept, a vehicle gearbox component, and a tool in medical diagnosis, with history, characteristics, examples and key distinctions.

Differential calculus: rates of change, derivatives, and applications Differential calculus Differential calculus studies instantaneous rates of change and tangent behavior of functions. It defines derivatives, basic computation rules, higher derivatives, multivariable ex…

Differential coefficient — historical name for the derivative Differential coefficient An older term for the derivative, the differential coefficient is the factor relating df to dx. This article explains its meaning, formal definition, properties, historical usage,…

Differential cryptanalysis: principles, history, and practical impact Differential cryptanalysis Overview of differential cryptanalysis: how input differences propagate, main techniques and variants, historical development, practical considerations, and defenses used in modern…