Wikipedia:WikiProject Mathematics/List of mathematics articles (O)

O-minimal theory -- O'Brien code I -- O'Brien code II -- O'Nan group -- O'Nan–Scott theorem -- O(n) -- O*-algebra -- Obconic -- Oberwolfach problem -- Object language -- Object of the mind -- Object theory -- Oblate spheroidal coordinates -- Oblate spheroidal wave function -- Oblique lattice -- Oblique projection -- Oblique reflection -- Observability -- Observability Gramian -- Observable subgroup -- Observable variable -- Observational equivalence -- Observational error -- Observational study -- Obstacle avoidance -- Obstacle problem -- Obstruction theory -- Obversion -- Occam's razor -- Occupancy frequency distribution -- Occupancy theorem -- Occurrences of Grandi's series -- Occurs check --

Ocean general circulation model -- Ockham algebra -- Octacontagon -- Octacube (sculpture) -- Octadecagon -- Octadecahedron -- Octagon -- Octagonal antiprism -- Octagonal bipyramid -- Octagonal number -- Octagonal prism -- Octagonal trapezohedron -- Octagram -- Octagrammic antiprism -- Octagrammic crossed-antiprism -- Octagrammic cupola -- Octagrammic prism -- Octahedral cupola -- Octahedral-dodecahedral honeycomb -- Octahedral-hexagonal tiling honeycomb -- Octahedral number -- Octahedral prism -- Octahedral pyramid -- Octahedral symmetry -- Octahedron -- Octahemioctahedron -- Octal -- Octal game -- Octal games -- Octant (solid geometry) -- Octave (electronics) -- Octic reciprocity -- Octomino -- Octonion -- Octonion algebra --

Odd cycle transversal -- Odd graph -- Odd greedy expansion -- Odd number -- Odd number theorem -- Odd Squad -- Odds -- Odds algorithm -- Odds and evens -- Odds and evens (hand game) -- Odds ratio -- Odia numerals -- Odious number -- Odlyzko–Schönhage algorithm -- Of the form -- Offered load -- Official statistics -- Offset binary -- Ogden's lemma -- Ogg's formula -- Ogive -- Ogive (statistics) -- Ohlson O-score -- Ohsawa–Takegoshi L2 extension theorem -- Oka coherence theorem -- Oka–Weil theorem -- Oka's lemma -- Okishio's theorem -- Okubo algebra -- Olaf Storaasli -- Olami–Feder–Christensen model --

Olbers' paradox -- Olech theorem -- OLGA (technology) -- Olimpíada Brasileira de Matemática -- Olimpíada Brasileira de Matemática das Escolas Públicas -- Olimpíada de Matemática do Grande ABC -- Oliver Sin -- Olog -- Oloid -- Olympiade Mathématique Belge -- OMDoc -- Omega and agemo subgroup -- Omega-categorical theory -- Omega constant -- Omega equation -- Omega function -- Omega-logic -- Omega ratio -- Omitted-variable bias -- Omnibus test -- Omnitruncated 5-simplex honeycomb -- Omnitruncated 6-simplex honeycomb -- Omnitruncated 7-simplex honeycomb -- Omnitruncated 8-simplex honeycomb -- Omnitruncated polyhedron -- Omnitruncated simplectic honeycomb -- Omnitruncated tesseractic honeycomb -- Omnitruncation -- On Conoids and Spheroids -- On Formally Undecidable Propositions of Principia Mathematica and Related Systems -- On-Line Encyclopedia of Integer Sequences -- On Numbers and Games -- On Sizes and Distances (Hipparchus) -- On Spirals -- On the Number of Primes Less Than a Given Magnitude -- On the Sphere and Cylinder --

One- and two-tailed tests -- One-dimensional space -- One-dimensional symmetry group -- One-form (differential geometry) -- One half -- One in ten rule -- One-key MAC -- One-parameter group -- One-relator group -- One-seventh area triangle -- One-shot deviation principle -- One-sided limit -- One Through Zero (The Ten Numbers) -- One-way analysis of variance -- One-way function -- One-way wave equation -- Ones' complement -- Online codes -- Online optimization -- Ono's inequality -- Onsager–Machlup function -- Onsager reciprocal relations -- Ontario Mathematics Olympiad -- Ontological maximalism -- Opaque set -- Opasnet -- Open and closed maps -- Open assessment -- Open book decomposition -- Open coloring axiom -- Open Energy Modelling Initiative -- Open energy system models -- Open formula -- Open-loop model -- Open mapping theorem -- Open mapping theorem (complex analysis) -- Open mapping theorem (functional analysis) -- Open Mathematics -- Open problem -- Open Problems in Mathematics -- Open set -- Open set condition -- Open-shop scheduling -- Open Systems & Information Dynamics -- OpenBLAS -- OpenIntro Statistics -- OpenMath -- OpenPlaG -- Oper (mathematics) -- Opera Omnia Leonhard Euler -- Operad -- Operad algebra -- Operand -- Operation (mathematics) -- Operational calculus -- Operational Research Society -- Operations research -- Operations Research (journal) -- Operations Research Society of South Africa -- Operator -- Operator (mathematics) -- Operator (physics) -- Operator algebra -- Operator associativity -- Operator ideal -- Operator K-theory -- Operator monotone function -- Operator norm -- Operator space -- Operator system -- Operator theory -- Operator topologies -- Opetope --

Opial property -- Opinion poll -- Opinion polling in the Philippine Senate election, 2010 -- Oppenheim conjecture -- Oppermann's conjecture -- Opposite -- Opposite category -- Opposite group -- Opposite ring -- Optic equation -- Optical axis -- Optical chaos -- Optical correlator -- Opticks -- Optimal apportionment -- Optimal computing budget allocation -- Optimal control -- Optimal design -- Optimal discriminant analysis -- Optimal estimation -- Optimal instruments -- Optimal matching -- Optimal projection equations -- Optimal stopping -- Optimal substructure -- Optimality criterion -- Optimistic knowledge gradient -- Optimization (computer science) -- OptimJ -- Option on realized variance -- Option on realized volatility -- Optional stopping theorem -- Options strategy --

Opuscula Mathematica -- OR gate -- Oracle complexity (optimization) -- Oracle machine -- Orbifold -- Orbifold notation -- Orbit (dynamics) -- Orbit capacity -- Orbit method -- Orbit modeling -- Orbit portrait -- Orbit trap -- Orbital integral -- Orbital momentum vector -- Orbital overlap -- Orbital stability -- Orbital state vectors -- Orbital velocity -- Orchard-planting problem -- Order (graph theory) -- Order (group theory) -- Order (journal) -- Order (mathematics) -- Order (number theory) -- Order (ring theory) -- Order-2 apeirogonal tiling -- Order-3-4 heptagonal honeycomb -- Order-3-5 heptagonal honeycomb -- Order-3-6 heptagonal honeycomb -- Order-3-7 heptagonal honeycomb -- Order-3-7 hexagonal honeycomb -- Order 3-7 kisrhombille -- Order-4 120-cell honeycomb -- Order-4 24-cell honeycomb -- Order-4 24-cell honeycomb honeycomb -- Order-4-3 pentagonal honeycomb -- Order-4-4 pentagonal honeycomb -- Order-4-5 pentagonal honeycomb -- Order-4-5 square honeycomb -- Order-4 dodecahedral honeycomb -- Order-4 heptagonal tiling -- Order-4 hexagonal tiling honeycomb -- Order-4 icosahedral honeycomb -- Order-4 octahedral honeycomb -- Order-4 pentagonal tiling -- Order-4 square hosohedral honeycomb -- Order-4 square tiling honeycomb -- Order-5 120-cell honeycomb -- Order-5-3 square honeycomb -- Order-5-4 square honeycomb -- Order-5 5-cell honeycomb -- Order-5 cubic honeycomb -- Order-5 dodecahedral honeycomb -- Order-5 hexagonal tiling honeycomb -- Order-5 icosahedral 120-cell honeycomb -- Order-5 octahedral honeycomb -- Order-5 pentagonal tiling -- Order-5 square tiling -- Order-5 tesseractic honeycomb -- Order-5 truncated pentagonal hexecontahedron -- Order-6-3 square honeycomb -- Order-6-4 square honeycomb -- Order-6-4 triangular honeycomb -- Order-6 cubic honeycomb -- Order-6 dodecahedral honeycomb -- Order-6 hexagonal tiling honeycomb -- Order-6 tetrahedral honeycomb -- Order-6 triangular hosohedral honeycomb -- Order-7-3 triangular honeycomb -- Order-7 cubic honeycomb -- Order-7 dodecahedral honeycomb -- Order-7 heptagonal tiling -- Order-7 heptagrammic tiling -- Order-7 square tiling -- Order-7 tetrahedral honeycomb -- Order-7 triangular tiling -- Order-7 truncated triangular tiling -- Order-8-3 triangular honeycomb -- Order and Chaos -- Order bound dual -- Order complete -- Order convergence -- Order dimension -- Order dual (functional analysis) -- Order embedding -- Order-extension principle -- Order-infinite-3 triangular honeycomb -- Order isomorphism -- Order of a kernel -- Order of a polynomial -- Order of accuracy -- Order of approximation -- Order of integration (calculus) -- Order of magnitude -- Order of operations -- Order polynomial -- Order polytope -- Order statistic -- Order summable -- Order theory -- Order topology -- Order topology (functional analysis) -- Order type -- Order unit -- Order-zero graph -- Ordered algebra -- Ordered Bell number -- Ordered exponential -- Ordered exponential field -- Ordered field -- Ordered geometry -- Ordered graph -- Ordered logit -- Ordered pair -- Ordered probit -- Ordered ring -- Ordered semigroup -- Ordered set -- Ordered set operators -- Ordered subset expectation maximization -- Ordered topological vector space -- Ordered vector space -- Orders of magnitude (probability) -- Ordinal analysis -- Ordinal arithmetic -- Ordinal association -- Ordinal collapsing function -- Ordinal date -- Ordinal definable set -- Ordinal logic -- Ordinal notation -- Ordinal number -- Ordinal numeral -- Ordinal numerical competence -- Ordinal Priority Approach -- Ordinal regression -- Ordinal sum -- Ordinary differential equation -- Ordinary least squares -- Ordinary singularity -- Ordination (statistics) --

Ore algebra -- Ore condition -- Ore extension -- Ore's theorem -- Oregonator -- Organon -- Orientability -- Orientation (geometry) -- Orientation (graph theory) -- Orientation (vector space) -- Orientation character -- Orientation entanglement -- Orientation of a vector bundle -- Orientation sheaf -- Oriented coloring -- Oriented matroid -- Oriented projective geometry -- Orientifold -- Origami Polyhedra Design -- Origamics -- Origin (mathematics) -- Original proof of Gödel's completeness theorem -- Orlicz–Pettis theorem -- Orlicz sequence space -- Orlicz space -- Ornstein isomorphism theorem -- Ornstein–Uhlenbeck operator -- Ornstein–Uhlenbeck process -- Ornstein–Zernike equation -- Orr–Sommerfeld equation --

Orthant -- Orthobifastigium -- Orthocentric system -- Orthocentric tetrahedron -- Orthocentroidal circle -- Orthocompact space -- Orthodiagonal quadrilateral -- Orthodox semigroup -- Orthogonal array -- Orthogonal basis -- Orthogonal complement -- Orthogonal convex hull -- Orthogonal coordinates -- Orthogonal diagonalization -- Orthogonal functions -- Orthogonal group -- Orthogonal matrix -- Orthogonal polynomials -- Orthogonal polynomials on the unit circle -- Orthogonal Procrustes problem -- Orthogonal symmetric Lie algebra -- Orthogonal trajectory -- Orthogonal transformation -- Orthogonal wavelet -- Orthogonality -- Orthogonality (mathematics) -- Orthogonality (term rewriting) -- Orthogonality principle -- Orthogonalization -- Orthographic projection -- Orthographic projection (cartography) -- Orthologic triangles -- Orthometric height -- Orthomorphism -- Orthonormal basis -- Orthonormal frame -- Orthonormal function system -- Orthonormality -- Orthopole -- Orthoptic (geometry) -- Orthostochastic matrix --

Oscillation -- Oscillation (mathematics) -- Oscillation theory -- Oscillator linewidth -- Oscillator representation -- Oscillatory integral -- Oscillatory integral operator -- Oscillon -- Osculant -- Osculate -- Osculating circle -- Osculating curve -- Osculating plane -- Oseen equations -- Oseledets theorem -- Osgood curve -- Osgood's lemma -- Osmund Lewry -- Ostomachion -- Ostrogradsky instability -- Ostrowski–Hadamard gap theorem -- Ostrowski numeration -- Ostrowski Prize -- Ostrowski's theorem -- Oswald Veblen Prize in Geometry -- Otis King -- Otsu's method -- Out in Science, Technology, Engineering, and Mathematics -- Out-of-bag error -- Out-of-kilter algorithm -- Out to Innovate -- Out(Fn) -- Outage probability -- Outcome (game theory) -- Outcome (probability) -- Outer automorphism group -- Outer billiards -- Outer measure -- Outer product -- Outer space (mathematics) -- Outermorphism -- Outerplanar graph -- Outlier -- Outline of algebra -- Outline of algebraic structures -- Outline of arithmetic -- Outline of calculus -- Outline of category theory -- Outline of combinatorics -- Outline of discrete mathematics -- Outline of geometry -- Outline of linear algebra -- Outline of logic -- Outline of mathematics -- Outline of probability -- Outline of regression analysis -- Outline of statistics -- Outline of trigonometry --

Oval -- Oval (projective plane) -- Overcategory -- Overcompleteness -- Overconvergent modular form -- Overdetermined system -- Overdispersion -- Overfitting -- Overfull conjecture -- Overfull graph -- Overlap (term rewriting) -- Overlap–add method -- Overlap coefficient -- Overlap–save method -- Overlapping circles grid -- Overlapping interval topology -- Overlapping subproblems -- Overring -- Oversampling and undersampling in data analysis -- Overspill -- Ovoid (polar space) -- Ovoid (projective geometry) -- Owen's T function -- Oxford Set of Mathematical Instruments --