Looking for math words that start with ‘i’? This article lists all the key terms you’ll need to know.

**Identity-**An element that, when combined with another element in an operation, leaves the other element unchanged.**Integer-**A whole number that can be positive, negative, or zero.**Integration-**The process of finding the integral of a function.**Inequality-**A mathematical statement that shows the relationship between quantities that are not equal.**Imaginary number-**A complex number in which the imaginary part is not zero.**Induction-**A method of mathematical proof typically used to establish a given statement for all natural numbers.**Isosceles-**A type of triangle with at least two equal sides.**Irrational number-**A number that cannot be expressed as a ratio of two integers.**Iteration-**The process of repeating a set of operations until a specific condition is met.**Incircle-**The largest circle that fits inside a polygon, touching all its sides.**Inflection-**A point on a curve at which the curvature changes sign.**Intercept-**The point where a line crosses an axis on a graph.**Interval-**A range of values between two specified limits.**Inradius-**The radius of an incircle.**Isometric-**Equal in measurements or dimensions.**Identity matrix-**A square matrix with ones on the diagonal and zeros elsewhere.**Inverse function-**A function that reverses the effect of the original function.**Interpolation-**The process of estimating unknown values that fall between known values.**Incidence-**The relationship between two figures when they share a common point.**Intersection-**The set of points common to two or more geometric configurations.**Infimum-**The greatest element that is less than or equal to each element of a subset in order theory.**Index-**A number or letter that indicates the position of an item in a sequence or set.**Isometry-**A transformation that preserves distances between points.**Improper fraction-**A fraction in which the numerator is greater than or equal to the denominator.**Icosagon-**A polygon with twenty sides.**Invariance-**Property of remaining unchanged under transformations.**Implicit function-**A function defined implicitly by an equation.**Ideal-**A special subset of a ring in algebra.**Involution-**A function that is its own inverse.**Initial value-**The starting value of a function or sequence.**Inhomogeneous-**A term describing differential equations where terms are not equal to zero.**Incidence matrix-**A matrix that shows the relationship between vertices and edges of a graph.**Injective-**A function that maps distinct elements to distinct elements.**Invariants-**Quantities that remain constant under transformations.**Incenter-**The center of an incircle.**Infinite series-**A sum of infinitely many terms.**Integral domain-**A type of ring with no zero divisors.**Increase-**To become greater in size, amount, or degree.**Interior angle-**An angle inside a polygon.**Intersecting lines-**Lines that cross at one point.**Inversely proportional-**A relationship where one quantity decreases as another increases.**Intermediate value-**Any value between two given values.**Isohedron-**A polyhedron with all faces the same shape and size.**Isomorphism-**A mapping that shows a one-to-one correspondence between sets that preserves structures.**Independent variable-**A variable whose variation does not depend on another.**Integers modulo n-**The set of integers 0 through n-1 under addition modulo n.**Indeterminate form-**An expression in calculus that does not define a value.**Iterative method-**A method that produces a sequence of approximations to the solution.**Index notation-**A representation of complex algebraic expressions using subscripts.**Interval notation-**A representation of sets of numbers as intervals.**Infinitesimal-**An infinitely small quantity.**Implicit differentiation-**A technique to find derivatives when a function is not given explicitly.**Idempotent-**An element that, when operated on by a certain function, yields itself.**Initial condition-**A value or set of values used to solve a differential equation.**Intersection point-**The point where two lines or curves meet.**Irrational equation-**An equation involving irrational numbers.**Iterated integral-**A multiple integral where one integration is performed after another.**Independent events-**Events whose outcomes do not affect each other.**Inverse matrix-**A matrix that, when multiplied with the original matrix, yields the identity matrix.**Involution algebra-**Algebra involving involution operations.**Isotropic-**Uniform in all directions.**Infimum norm-**The greatest lower bound of a function.**Inner product-**A generalization of the dot product to abstract vector spaces.**Interval graph-**A graph where intervals of the real line are vertices and edges represent overlapping intervals.**Initial side-**The starting position of a ray in an angle.**Induced subgraph-**A subset of a graph formed by deleting some vertices and edges.**Irreducible fraction-**A fraction in simplest form.**Infinity-**A concept describing something without bound or end.**Inductive reasoning-**A method of reasoning in which a generalization is made based on observed patterns.**Isosurface-**A three-dimensional surface representing points of a constant value within a volume of space.**Invariant theory-**A study of algebraic forms that remain constant under transformations.**Immediate successor-**The next element in a well-ordered set.**Integral calculus-**A branch of calculus focused on the concept of the integral and its applications.**Injectivity-**A property of functions where each input is mapped to a unique output.**Isogonal-**Referring to angles that are equal.**Isotone-**A function or relation that preserves order.**Infix notation-**Normal arithmetic notation where the operator is placed between operands.**Invertible-**Capable of being inverted or having an inverse function.**Infimum element-**The least upper bound in order theory.**Irreducible polynomial-**A polynomial that cannot be factored into lower-degree polynomials.

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