- I
- I-adic topology
- Iamblichus
- Iamond
- Iban number
- IBN or Ibn
- Icosagon
- Icosahedral group
- Icosahedron
- Icosidodecadodecahedron
- Icosidodecahedron
- Icositetrachoron
- Icositruncated dodecadodecahedron
- Ideal
- Ideal (ring theory)
- Ideal class
- Ideal number
- Ideal point
- Ideal quotient
- Ideal triangle
- Idele
- Idempotency
- Idempotent
- Idempotent matrix
- Idempotent semi-ring
- Idempotent semiring
- Identically zero
- Identity
- Identity
- Identity element or Identity Element
- Identity function
- Identity map
- Identity matrix
- Identity operator
- Identity theorem
- Identity transformation
- Identric mean
- Idèle or Idele
- Idèle class character
- IF-logic or If-logic
- Iff or IFF
- Ill defined
- Ill-conditioned matrix
- Ill-posed problems
- Illusion
- Im
- Image
- Image (mathematics)
- Imaginary
- Imaginary axis
- Imaginary line
- Imaginary number
- Imaginary part
- Imaginary point
- Imaginary quadratic field
- Imaginary unit
- Immanant
- Immanent
- Immersion
- Impartial game
- Implication
- Implicit differentiation
- Implicit function
- Implicit function theorem or Implicit Function Theorem
- Implies
- Impossible figure
- Impossible fork
- Impossible triangle
- Impossible tribar
- Impredicative
- Improper distribution
- Improper fraction
- Improper integral
- Improper limits
- Improper rotation
- Imputation
- In-place sorting algorithm
- Inaccessible cardinal
- Inaccessible cardinals axiom
- Inadmissible
- Incenter
- Incidence
- Incidence axioms
- Incidence geometry
- Incidence graph
- Incidence matrix
- Incidence structure
- Incident
- Incircle
- Inclusion map
- Inclusion-exclusion principle
- Inclusive disjunction
- Incomplete beta function
- Incomplete beta-function
- Incomplete elliptic integral of the first kind
- Incomplete elliptic integral of the second kind
- Incomplete elliptic integral of the third kind
- Incomplete gamma function or Incomplete Gamma function
- Incomplete gamma-function
- Incompleteness
- Inconic
- Inconsistency
- Increasing function
- Increasing sequence
- Indecomposable
- Indecomposable continuum
- Indecomposable distribution
- Indecomposable module
- Indefinite integral
- Indefinite matrix
- Indegree
- Independence
- Independence number
- Independent events
- Independent increment
- Independent set
- Indeterminate
- Indeterminate (variable)
- Indeterminate equation
- Indeterminate form
- Index
- Index formulas
- Index number
- Index of a subgroup
- Index set
- Index theory
- Indicator
- Indicator function
- Indicatrix
- Indicial equation
- Indifference Principle or Indifference principle
- Indiscrete topology
- Individual
- Induced representation
- Induced subgraph
- Induction
- Inductive bias
- Inductive definition
- Inductive dimension
- Inductive limit
- Inductive set
- Inductive set (axiom of infinity)
- Inductive topology
- Inequality
- Inequation
- Inertial degree
- Inexact differential
- Inf
- Inference rule
- Infimum
- Infimum limit
- Infinite
- Infinite descent
- Infinite game
- Infinite group
- Infinite matrix
- Infinite product
- Infinite Series or Infinite series
- Infinite set
- Infinite-dimensional space
- Infinitesimal
- Infinitesimal calculus
- Infinitesimal character
- Infinitesimal operator
- Infinitesimal rotation
- Infinitude of primes
- Infinity
- Infix notation
- Inflection point
- Informant
- Information
- Information dimension
- Information Entropy or Information entropy
- Information set
- Information Theory or Information theory
- Information-based complexity
- Ingrid Daubechies
- Inhabited set
- Initial conditions
- Initial object
- Initial ordinal
- Initial segment
- Initial topology
- Initial value problem
- Injection
- Injective
- Injective function
- Injective hull
- Injective map
- Injective module
- Injective object
- Injective resolution
- Injectivity
- Inner automorphism
- Inner automorphism group
- Inner function
- Inner product
- Inner product space or Inner Product Space
- Inradius
- Inscribe
- Inscribed
- Inscribed angle
- Inscriptable quadrilateral
- Insertion sort
- Inside
- Insphere
- Instanton
- Int
- Integer
- Integer division
- Integer factorization
- Integer lattice
- Integer Matrix or Integer matrix
- Integer part
- Integer partition
- Integer polynomial
- Integer programming
- Integer sequence
- Integer value
- Integers
- Integrable
- Integrable function
- Integrable system
- Integral
- Integral basis
- Integral calculus
- Integral closure
- Integral curve
- Integral domain
- Integral equation
- Integral extension
- Integral geometry
- Integral Hodge conjecture
- Integral Hodge conjectures
- Integral ideal
- Integral kernel
- Integral logarithm
- Integral manifold
- Integral of motion
- Integral operator
- Integral part
- Integral polynomial
- Integral ring
- Integral sign
- Integral sine
- Integral test
- Integral transform
- Integrally closed
- Integrand
- Integrate
- Integrating factor
- Integration
- Integration by parts
- Integration by substitution or Integration by Substitution
- Integration constant
- Integration on manifolds
- Integro-differential equation
- Intension
- Intercept
- Intercession
- Interest
- Interest rate
- Interior
- Interior angle
- Interior point method
- Interior point of a set
- Interior product
- Interleave sequence
- Intermediate Jacobian
- Intermediate logic
- Intermediate value theorem or Intermediate Value Theorem
- Internal node
- Internal waves
- Internet
- Interpolation
- Interpolation formula
- Interpretation
- Interprime
- Interquartile Range or Interquartile range
- Intersecting lines
- Intersection
- Intersection (set theory)
- Intersection array
- Intersection graph
- Intersection homology
- Intersection number
- Intersection theory
- Intersphere
- Intertwining operator
- Interval
- Interval analysis
- Interval arithmetic
- Interval estimator
- Interval graph
- Interval halving
- Interval halving converges linearly
- Interval order
- Intrinsic curvature
- Intuitionism
- Intuitionistic arithmetic
- Intuitionistic logic
- Intuitionistic propositional calculus
- Invariance of dimension
- Invariance theorem
- Invariant
- Invariant differential operator
- Invariant factor
- Invariant measure
- Invariant polynomial
- Invariant series
- Invariant subgroup
- Invariant subspace
- Invariant subspace problem
- Invariant theory
- Inverse
- Inverse cosecant
- Inverse cosine
- Inverse cotangent
- Inverse filter
- Inverse Fourier transform or Inverse fourier transform
- Inverse function
- Inverse function theorem
- Inverse Galois problem
- Inverse Gaussian distribution or Inverse gaussian distribution
- Inverse hyperbolic cosecant
- Inverse hyperbolic cosine
- Inverse hyperbolic cotangent
- Inverse hyperbolic functions
- Inverse hyperbolic secant
- Inverse hyperbolic sine
- Inverse hyperbolic tangent
- Inverse Laplace transform or Inverse laplace transform
- Inverse limit
- Inverse map
- Inverse mapping
- Inverse matrix
- Inverse problem
- Inverse problem of Galois theory
- Inverse proportion
- Inverse quadratic interpolation
- Inverse scattering method
- Inverse secant
- Inverse semigroup
- Inverse sine
- Inverse system
- Inverse tangent
- Inverse tangent integral
- Inverse trigonometric functions
- Inversely proportional
- Inversion
- Inversive geometry
- Inversive plane
- Inverted snub dodecadodecahedron
- Invertible
- Invertible element
- Invertible matrix or Invertible Matrix
- Invertible sheaf
- Involutary ring
- Involute
- Involution
- Involution algebra
- Involutive algebra
- Involutive distribution
- Involutory
- Irrational
- Irrational Number or Irrational number
- Irrationality measure
- Irreducible
- Irreducible component
- Irreducible element
- Irreducible fraction
- Irreducible module
- Irreducible polynomial
- Irreducible representation
- Irreducible semiperfect number
- Irreducible variety
- Irreflexive
- Irregular prime
- Irregular singular point
- Irregular singularity
- Irregularity
- Irrotational field
- Isarithm
- ISBN or Isbn
- Ishango bone or Ishango Bone
- Ising model or Ising Model
- Island
- Isocline
- Isogeny
- Isogonal
- Isogonal conjugate
- Isogonal trajectory
- Isograph
- Isol
- Isolated point
- Isolated singular point
- Isolated singularity
- Isolated subgroup
- Isometric
- Isometric immersion
- Isometric mapping
- Isometry
- Isomorphic
- Isomorphic graphs
- Isomorphism
- Isomorphism of categories
- Isomorphism problem
- Isomorphism theorem
- Isomorphism-closed subcategory
- Isoperimetry
- Isopleth
- Isosceles right triangle
- Isosceles trapezium
- Isosceles trapezoid
- Isosceles triangle or Isosceles Triangle
- Isospectral
- Isosurface
- Isothermal coordinates
- Isothetic
- Isotomic conjugate
- Isotope
- Isotopy
- Isotropic line
- Isotropic submanifold
- Isotropy group
- Isthmus
- Iterate
- Iterated exponential
- Iterated function
- Iterated Function System or Iterated function system
- Iterated integral
- Iterated loop space
- Iterated map
- Iteration
- Iteration algorithm
- Iteration methods
- Iterator
- Itô formula
- Itô integral
- Itô process
- Itô's formula
- Itô's Lemma or Itô's lemma
- Ivan Niven
- Ivan Privalov
- Ivan Vinogradov
- Iverson bracket
- Iwasawa decomposition
- Iwasawa theorem
- Iwasawa theory
- Iwasawa's theorem