- R
- R-algebra
- R-group
- R-module
- R-n
- Raabe's test
- Rabbit Sequence or Rabbit sequence
- Rabdology
- Rabin-Miller strong pseudoprime test or Rabin-miller strong pseudoprime test
- Rabinovich-Fabrikant equation
- Racah W-coefficient
- Rademacher's theorem
- Radial basis function
- Radial line
- Radian
- Radiation conditions
- Radical
- Radical (mathematics)
- Radical axis
- Radical center
- Radical of an ideal
- Radical of an integer
- Radical of rings and algebras
- Radical root
- Radicand
- Radius
- Radius of convergence
- Radius of curvature
- Radius of Gyration or Radius of gyration
- Radius vector
- Radix
- Radix sort
- Rado's theorem or Rado's Theorem
- Radon integral
- Radon measure
- Radon Transform or Radon transform
- Radon's lemma
- Radon's theorem
- Radon-Nikodym Derivative or Radon-Nikodym derivative
- Radon-Nikodym theorem or Radon-Nikodym Theorem or Radon-Nikodým theorem
- Ramanujan
- Ramanujan Constant or Ramanujan constant
- Ramanujan continued fractions
- Ramanujan hypothesis
- Ramanujan prime
- Ramanujan sum
- Ramanujan theta functions
- Ramanujan's hypothesis
- Ramanujan's square equation
- Ramanujan's sum
- Ramanujan's tau function
- Ramanujan-Nagell equation
- Ramanujan-Petersson conjecture
- Ramanujan-Soldner constant
- Ramification group
- Ramification index
- Ramification point
- Ramp function
- Ramsey Number or Ramsey number
- Ramsey numbers
- Ramsey theorem
- Ramsey Theory or Ramsey theory
- Ramsey's theorem or Ramsey's Theorem
- Random
- Random allocation
- Random distribution
- Random dot stereogram
- Random element
- Random event
- Random field
- Random function
- Random graph
- Random mapping
- Random matrix
- Random number
- Random numbers
- Random permutation
- Random sequence
- Random variable or Random Variable
- Random variate
- Random vector
- Random walk
- Random Walk--1-Dimensional
- Random Walk--2-Dimensional
- Random Walk--3-Dimensional
- Randomization
- Randomization test
- Range
- Range (mathematics)
- Range problem
- Range voting
- Rank
- rank
- Rank of a Lie group
- Rank of an elliptic curve
- Rank test
- Rank-nullity theorem
- Rankin’s method
- Rao-Cramér inequality
- Rate of convergence
- Rate of return
- Ratio
- Ratio Distribution or Ratio distribution
- Ratio test
- Rational
- Rational canonical form
- Rational curve
- Rational diagonal
- Rational domain
- Rational function
- Rational integer
- Rational mapping
- Rational number or Rational Number
- Rational point
- Rational representation
- Rational root theorem
- Rational singularity or Rational Singularity
- Rational surface
- Rational tangles
- Rational triangle
- Rational variety
- Rationalise
- Rationals
- Raw moment
- Ray
- Rayleigh distribution
- Rayleigh quotient
- Rayleigh-Taylor instability
- Re or RE
- Reaction-diffusion equation
- Real Analysis or Real analysis
- Real analytic function
- Real and complex embeddings
- Real axis
- Real closed field
- Real exponential function
- Real form
- Real function or Real Function
- Real line
- Real manifold
- Real matrix
- Real measure
- Real number
- Real Numbers or Real numbers
- Real part
- Real polynomial
- Real projective plane
- Real projective space
- Real quadratic field
- Real space
- Real tree
- Real variable
- Real vector
- Real vector bundle
- Real vector space
- Real-valued function
- Realizability
- Realization
- Realizer
- Reals
- Rearrangement inequality
- Reciprocal
- Reciprocal difference
- Reciprocal Fibonacci Constant or Reciprocal Fibonacci constant
- Reciprocal matrix
- Reciprocal polynomial
- Reciprocation
- Reciprocity law
- Reciprocity laws
- Reciprocity Theorem or Reciprocity theorem
- Recognize
- Rectangle
- Rectangle function
- Rectangle rule
- Rectangular Coordinates or Rectangular coordinates
- Rectangular distribution
- Rectangular parallelepiped
- Rectifiable
- Rectifiable curve
- Rectifiable Set or Rectifiable set
- Rectification
- Recurrence equation
- Recurrence plot
- Recurrence relation
- Recurrent point
- Recurrent relation
- Recurring decimal
- Recursion
- Recursion Theorem or Recursion theorem
- Recursive definition
- Recursive function
- Recursive relation
- Recursive Sequence or Recursive sequence
- Recursive set
- Recursively enumerable set or Recursively Enumerable Set
- Red-black tree or Red-Black Tree
- Redmond-Sun conjecture
- Reduce
- Reduced echelon form
- Reduced residue system
- Reduced ring
- Reduced row echelon form
- Reduced scheme
- Reducible
- Reducible representation
- Reductio ad absurdum
- Reduction of Order or Reduction of order
- Reduction of structure group
- Reductive group
- Reductive Lie algebra
- Redundancy
- Ree group
- Reeb foliation
- Reed-Sloane algorithm
- Reef Knot or Reef knot
- Refactorable number
- Refal
- Refinement
- Reflection
- Reflection Formula or Reflection formula
- Reflection group
- Reflection principle
- Reflection Relation or Reflection relation
- Reflective subcategory
- Reflector
- Reflex angle
- Reflexive
- Reflexive Banach space
- Reflexive space
- Reflexivity
- Refraction
- Region
- Register machine
- Regression
- Regression analysis
- Regression model
- Regression to the Mean or Regression to the mean
- Regula falsi
- Regular element
- Regular expression or Regular Expression
- Regular function
- Regular grammar
- Regular graph
- Regular group action
- Regular homotopy
- Regular isotopy
- Regular language
- Regular local ring
- Regular matrix
- Regular measure
- Regular Number or Regular number
- Regular octagon
- Regular open set
- Regular pentagon
- Regular polygon
- Regular polygons
- Regular polyhedra
- Regular polyhedron
- Regular polytope
- Regular prime
- Regular prime number
- Regular representation
- Regular ring
- Regular semigroup
- Regular sequence
- Regular singular point
- Regular singularity
- Regular space
- Regular tessellation
- Regularity axiom
- Regularity lemma
- Regularization
- Regularized beta function
- Regularized gamma function or Regularized Gamma function
- Regularly open
- Regulator
- Regulator of an algebraic number field
- Regulus
- Reidemeister moves
- Related rates
- Relation
- Relation (mathematics)
- Relational structure
- Relative complement
- Relative Degree
- Relative entropy
- Relative error
- Relative Frequency or Relative frequency
- Relative homology
- Relative homology groups
- Relative interior
- Relative topology
- Relatively compact
- Relatively compact subspace
- Relatively prime
- Relatively-compact set
- Relativistic dynamics
- Relativistic invariance
- Relativity principle
- Relativity theory
- Relaxation oscillation
- Reliability theory
- Rellich selection theorem
- Remainder
- Remainder of an integer
- Remainder term
- Remainder Theorem or Remainder theorem
- Remez algorithm
- Remez exchange algorithm
- Removable set
- Removable singular point
- Removable singularity
- Rencontres number
- Renewal theory
- Renormalization
- Repdigit
- Repeated integral
- Repeating Decimal or Repeating decimal
- Repfigit number
- Replica
- Replicate
- Representable functor
- Representation
- Representation of a finite group
- Representation of a group
- Representation of a Lie algebra
- Representation of the symmetric groups
- Representation theory
- Representations of Lie algebras
- Representations of Lie groups
- Reproducing kernel
- Reproducing-kernel Hilbert space
- Reptile
- Repunit
- Resampling statistics
- Residual
- Residual set
- Residually-finite group
- Residue
- Residue (complex analysis)
- Residue class
- Residue field
- Residue of an analytic function
- Residue Theorem or Residue theorem
- Resistance distance
- Resolution
- Resolution of singularities
- Resolution of the identity
- Resolution principle
- Resolve
- Resolvent
- Resolvent set
- Resonance
- Restricted direct product
- Restricted representation
- Resultant
- Retract
- Retraction
- Reuleaux polygon
- Reuleaux Tetrahedron or Reuleaux tetrahedron
- Reuleaux Triangle or Reuleaux triangle
- Reve's puzzle
- Reversal
- Reverse Polish notation or Reverse polish notation or Reverse Polish Notation
- Reversible prime
- Reversion of series
- Reversion to the Mean or Reversion to the mean
- Rewriting system
- Reynolds number
- Reynolds transport theorem
- Rhetoric
- Rhind Papyrus or Rhind papyrus
- Rhomb
- Rhombic dodecahedron
- Rhombic enneacontahedron
- Rhombic icosahedron
- Rhombic triacontahedron
- Rhombicosahedron
- Rhombicosidodecahedron
- Rhombicuboctahedron
- Rhombidodecadodecahedron
- Rhombitruncated cuboctahedron
- Rhombitruncated Icosidodecahedron or Rhombitruncated icosidodecahedron
- Rhombohedron
- Rhomboid
- Rhombus
- Rhumb Line or Rhumb line
- Ribbon knot
- Ribet's theorem
- Riccati differential equation
- Riccati equation
- Riccati-Bessel function
- Riccati-Bessel functions
- Ricci curvature
- Ricci curvature tensor
- Ricci flow
- Ricci tensor
- Rice distribution
- Rice's Theorem or Rice's theorem
- Richard Feynman or Richard feynman
- Richard paradox or Richard Paradox
- Richard Stanley
- Richard's Paradox or Richard's paradox
- Richardson extrapolation
- Rickart ring
- Ridge
- Riemann conditions
- Riemann curvature tensor
- Riemann differential equation
- Riemann function
- Riemann geometry
- Riemann hypotheses
- Riemann Hypothesis or Riemann hypothesis
- Riemann integral
- Riemann lemma
- Riemann mapping theorem or Riemann Mapping Theorem
- Riemann multiple integral
- Riemann P-differential equation
- Riemann P-series
- Riemann series theorem
- Riemann space
- Riemann sphere
- Riemann sum or Riemann Sum
- Riemann surface or Riemann Surface
- Riemann tensor
- Riemann theta function
- Riemann theta-function
- Riemann Xi function or Riemann xi function
- Riemann Xi-Function or Riemann xi-function
- Riemann zeta function or Riemann Zeta Function
- Riemann zeta function zeros
- Riemann zeta-function
- Riemann-Christoffel curvature tensor
- Riemann-Christoffel tensor
- Riemann-Hilbert problem
- Riemann-Hurwitz formula
- Riemann-Kempf singularity theorem
- Riemann-Lebesgue lemma or Riemann-Lebesgue Lemma
- Riemann-Roch theorem or Riemann-Roch Theorem
- Riemann-Roch theorem for algebraic surfaces
- Riemann-Stieltjes integral or Riemann-Stieltjes Integral
- Riemann-von Mangoldt formula
- Riemannian connection
- Riemannian curvature
- Riemannian geometry
- Riemannian manifold
- Riemannian metric
- Riemannian submersion
- Riesel number
- Riesel problem
- Riesz basis
- Riesz potential
- Riesz representation theorem
- Riesz sequence
- Riesz space
- Riesz theorem
- Riesz's theorem
- Riesz-Fischer theorem or Riesz-Fischer Theorem
- Riffle
- Rig
- Rigged Hilbert space or Rigged hilbert space
- Rigged manifold
- Right Angle or Right angle
- Right ascension or Right Ascension
- Right circular cone
- Right circular cylinder
- Right coset
- Right cylinder
- Right eigenvector
- Right hand rule
- Right ideal
- Right transversal
- Right triangle
- Right-hand rule
- Right-handed coordinate system
- Rigid
- Rigid analytic space
- Rigid motion
- Rigidity
- Rigidity theorem
- Rigorous
- Ring (mathematics)
- Ring extension
- Ring homomorphism
- Ring of endomorphisms
- Ring of fractions
- Ring of integers
- Ring of polynomials
- Ring of sets
- Ring spectrum
- Ring Theory or Ring theory
- Ring torus
- Ring unit
- Ring with identity
- Ringed space
- Riquier
- Risch algorithm
- Rise
- Rising factorial
- Risk theory
- Ritz method
- RK4
- RMS or Rms
- Robbins algebra
- Robbins conjecture
- Robbins constant
- Robert Calderbank
- Robertson-Seymour Theorem or Robertson-Seymour theorem
- Robertson–Seymour theorem
- Robin boundary conditions
- Robin's theorem
- Robinson projection
- Robust statistics
- Rodrigues formula
- Rodrigues' rotation formula
- Rogers-Ramanujan identities
- Rogers-Ramanujan identity
- Rolle theorem
- Rolle's theorem or Rolle's Theorem
- Roller
- Roman numerals or Roman Numerals
- Roman Surface or Roman surface
- Romberg integration
- Romberg method
- Ronald Graham
- Root or ROOT
- Root (mathematics)
- Root group
- Root lattice
- Root node or Root Node
- Root of unity
- Root system
- Root test
- Root vector
- Root-finding algorithm
- Root-mean-square
- Rooted graph
- Rooted tree
- Roots
- Rose
- Rosenbrock function
- Rosser's theorem
- Rotation
- Rotation formula
- Rotation group
- Rotation matrix
- Rotation number
- Rotation of a vector field
- Rotation operator
- Roth's theorem
- Rotoinversion
- Rotor
- Rotunda
- Rouché theorem
- Rouché's theorem
- Rough number
- Roulette
- Round
- Round function
- Round number
- Round Robin tournament or Round robin tournament
- Rounded rectangle
- Rounding
- Rounding error
- Roundness
- Roundoff error
- Route
- Routh theorem
- Routh's theorem
- Routh-Hurwitz theorem
- Row echelon form
- Row space
- Row vector
- Row-reduced echelon form
- RPN or Rpn
- RSA or Rsa
- RSA encryption or Rsa encryption
- RSA number
- Rubik's Clock or Rubik's clock
- Rubik's cube or Rubik's Cube
- Rudvalis group
- Rule
- Rule 110
- Rule 30
- Rule of 72
- Rule of inference
- Rule of nines
- Rule of signs
- Ruled surface or Ruled Surface
- Ruler
- Ruler and compass
- Ruling
- Rumors
- Rumors (science)
- Run
- Run-length encoding
- Runge theorem
- Runge's theorem or Runge's Theorem
- Runge-Kutta method or Runge-kutta method
- Running average
- Running knot
- Running time
- Russell paradox
- Russell's antinomy
- Russell's paradox or Russell's Paradox
- Russian multiplication
- Russian Roulette or Russian roulette
- Ruth Bari
- Ruth Lawrence or Ruth lawrence
- Ruth Moufang or Ruth moufang
- Ruth-Aaron pair
- Rényi entropy
- Rényi information
- Rózsa Péter or Rózsa péter
- Rössler Attractor or Rössler attractor
