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 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 Regular string, a binary string in which the one-density in any long consecutive substring is close to the one-density in the whole string 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