# Regular

Regular may refer to:

## Arts, entertainment, and media
### Music

* "Regular" (Badfinger song)
* Regular tunings of stringed instruments, tunings with equal intervals between the paired notes of successive open strings

### Other uses in arts, entertainment, and media

* Regular character, a main character who appears more frequently and/or prominently than a recurring character
* Regular division of the plane, a series of drawings by the Dutch artist M. C. Escher which began in 1936

## Language

* Regular inflection, the formation of derived forms such as plurals in ways that are typical for the language
** Regular verb
* Regular script, the newest of the Chinese script styles

## Mathematics
### Algebra and number theory

* Regular category, a kind of category that has similarities to both Abelian categories and to the category of sets
* Regular chains in computer algebra
* Regular element (disambiguation), certain kinds of elements of an algebraic structure
* Regular extension of fields
* Regular ideal (multiple definitions)
* Regular Lie group
* Regular matrix (disambiguation)
* Regular monomorphisms and regular epimorphisms, monomorphisms (resp. epimorphisms) which equalize (resp. coequalize) some parallel pair of morphisms
* Regular numbers, numbers which evenly divide a power of 60
* Regular p-group, a concept capturing some of the more important properties of abelian p-groups, but general enough to include most "small" p-groups
* Regular prime, a prime number p > 2 that does not divide the class number of the p-th cyclotomic field
* The regular representation of a group G, the linear representation afforded by the group action of G on itself
* Regular ring, a ring such that all its localizations have Krull dimension equal to the minimal number of generators of the maximal ideal
** von Neumann regular ring, or absolutely flat ring (unrelated to the previous sense)
* Regular semi-algebraic systems in computer algebra
* Regular semigroup, related to the previous sense
* *-regular semigroup

### Analysis

* Borel regular measure
* Cauchy-regular function (or Cauchy-continuous function,) a continuous function between metric spaces which preserves Cauchy sequences
* Regular functions, functions that are analytic and single-valued (unique) in a given region
* Regular measure, a measure for which every measurable set is "approximately open" and "approximately closed"
* The regular part, of a Laurent series, the series of terms with positive powers
* Regular singular points, in theory of ordinary differential equations where the growth of solutions is bounded by an algebraic function
* Regularity, the degree of differentiability of a function
* Regularity conditions arise in the study of first-class constraints in Hamiltonian mechanics
* Regularity of an elliptic operator
* Regularity theory of elliptic partial differential equations

### Combinatorics, discrete math, and mathematical computer science

* Regular algebra, or Kleene algebra
* Regular code, an algebraic code with a uniform distribution of distances between codewords
* Regular expression, a type of pattern describing a set of strings in computer science
* Regular graph, a graph such that all the degrees of the vertices are equal
** Szemerédi regularity lemma, some random behaviors in large graphs
* Regular language, a formal language recognizable by a finite state automaton (related to the regular expression)
* Regular map (graph theory), a symmetric tessellation of a closed surface
* Regular matroid, a matroid which can be represented over any field
* Regular paperfolding sequence, also known as the dragon curve sequence
* Regular tree grammar

### Geometry

* Castelnuovo–Mumford regularity of a coherent sheaf
* Closed regular sets in solid modeling
* Irregularity of a surface in algebraic geometry
* Regular curves
* Regular grid, a tesselation of Euclidean space by congruent bricks
* Regular map (algebraic geometry), a map between varieties given by polynomials
* Regular point, a non-singular point of an algebraic variety
* Regular point of a differentiable map, a point at which a map is a submersion
* Regular polygons, polygons with all sides and angles equal
** Regular polyhedron, a generalization of a regular polygon to higher dimensions
** Regular polytope, a generalization of a regular polygon to higher dimensions
* Regular skew polyhedron

### Logic, set theory, and foundations

* Axiom of Regularity, also called the Axiom of Foundation, an axiom of set theory asserting the non-existence of certain infinite chains of sets
* Partition regularity
* Regular cardinal, a cardinal number that is equal to its cofinality
* Regular modal logic

### Probability and statistics

* Regular conditional probability, a concept that has developed to overcome certain difficulties in formally defining conditional probabilities for continuous probability distributions
* Regular stochastic matrix, a stochastic matrix such that all the entries of some power of the matrix are positive

### Topology

* Free regular set, a subset of a topological space that is acted upon disjointly under a given group action
* Regular homotopy
* Regular isotopy in knot theory, the equivalence relation of link diagrams that is generated by using the 2nd and 3rd Reidemeister moves only
* Regular space (or $T_{3}$) space, a topological space in which a point and a closed set can be separated by neighborhoods

## Organizations

* Regular army for military usage
* Regular Baptists, an 18th-century American and Canadian Baptist group
* Regular clergy, members of a religious order subject to a rule of life
* Regular Force for usage in the Canadian Forces
* Regular Masonic jurisdictions, or regularity, refers to the constitutional mechanism by which Freemasonry Grand Lodges or Grand Orients give one another mutual recognition

## People

* Moses Regular (born 1971), America football player

## Science and social science

* Regular bowel movements, the opposite of constipation
* Regular economy, an economy characterized by an excess demand function whose slope at any equilibrium price vector is non-zero
* Regular moon, a natural satellite that has low eccentricity and a relatively close and prograde orbit
* Regular solutions in chemistry, solutions that diverge from the behavior of an ideal solution only moderately

## Other uses

* Regular customer, a person who visits the same restaurant, pub, store, or transit provider frequently
* Regular (footedness) in boardsports, a stance in which the left foot leads