Wikipedia:Missing science topics/ExistingMathO
- O
- O'Nan group
- O-minimal
- O-minimality
- O-notation
- O-symbol
- Oban number
- Obelisk
- Obelus
- Object
- Object language
- Objective function
- Oblate ellipsoid
- Oblate spheroid
- Oblateness
- Obliquity of the ecliptic
- Oblong number
- Observability
- Obstruction
- Obtuse angle
- Obtuse triangle
- Occam's Razor or Occam's razor
- Occultation
- Octachoron
- Octagon
- Octagonal number
- Octagonal prism
- Octagram
- Octahedral number
- Octahedron
- Octahemioctahedron
- Octal
- Octant
- Octave
- Octillion
- Octodecillion
- Octonion
- Octothorpe
- Odd function
- Odd number
- Odd order theorem
- Odd permutation
- Odd prime
- Odds
- Odds ratio
- ODE or Ode
- Odious number
- Ogive
- OLS
- Omega constant
- Omega Function or Omega function
- Omega-consistency
- "Omega-squared" distribution or "omega-squared" distribution
- Omino
- One or ONE
- One and only one
- One way function
- One-form
- One-parameter subgroup
- One-point compactification
- One-sided ideal
- One-sided limit
- One-to-one
- One-to-one correspondence
- One-way function
- One-way hash function
- Onto
- Open
- Open ball
- Open cover
- Open disk
- Open interval
- Open map
- Open mapping
- Open mapping theorem
- Open neighborhood
- Open problems
- Open set
- Open-mapping theorem
- Operad
- Operand
- Operation
- Operations Research or Operations research
- Operator
- Operator norm
- Operator spectrum
- Operator Theory or Operator theory
- Operator topology
- Opposite ring
- Opposition
- Optical Illusion or Optical illusion
- Optimal control
- Optimal Golomb Ruler or Optimal Golomb ruler
- Optimization
- Optimization theory
- Optimum
- Option pricing
- OR or Or
- Oracle
- Orbifold
- Orbit
- Orbit-counting theorem
- Order
- Order isomorphic
- Order of magnitude
- Order of operations
- Order relation
- Order statistic
- Order statistics
- Order topology
- Order type
- Ordered field
- Ordered group
- Ordered list
- Ordered pair
- Ordered ring
- Ordered set
- Ordering
- Ordinal
- Ordinal addition
- Ordinal exponentiation
- Ordinal multiplication
- Ordinal Number or Ordinal number
- Ordinary Differential Equation or Ordinary differential equation
- Ordinary generating function
- Ordinate
- Ore condition
- Ore domain
- Ore number
- Ore's theorem
- Orientable manifold
- Orientable surface
- Orientation
- Orientation-preserving
- Origami
- Origin
- Ornstein-Uhlenbeck process
- Orthic circle
- Orthic triangle
- Orthocenter
- Orthocentre
- Orthocentric system
- Orthodrome
- Orthogonal
- Orthogonal basis
- Orthogonal complement
- Orthogonal functions
- Orthogonal group
- Orthogonal Latin squares or Orthogonal latin squares
- Orthogonal matrix
- Orthogonal polynomials
- Orthogonal projection
- Orthogonal set
- Orthogonal subspaces
- Orthogonal system
- Orthogonal trajectory
- Orthogonal transformation
- Orthogonality
- Orthogonality relations
- Orthogonalization
- Orthographic projection
- Orthonormal basis
- Orthonormal set
- Orthonormality
- Orthoplex
- Orthotomic
- Osborne's rule
- Oscillation
- Harmonic oscillator or Harmonic Oscillator
- Osculate
- Osculating circle
- Osculating curves
- Osculating plane
- Osculation
- Ostrowski's theorem
- Outcome
- Outdegree
- Outer automorphism
- Outer automorphism group
- Outer measure
- Outer product
- Outlier
- Outside
- Oval
- Ovals of Cassini
- Over
- Overdamping
- Overdispersion
- Overhand knot
- Oversampling
- Ovoid