Welcome to a wonderful list of math words that start with I.

How many math words begin with the letter I? It could be a gazillion if you put the negative prefix in- in front of other Math words. Look below for most of the I Math words that I've ever used for the K-6 levels. I have kept a running list for years.

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Teaching the prefix in- will help your students see that it changes the meaning of words. It depends, too, on which meaning in- is using, too.

Sometimes in- means in as a preposition as with input and inflection, but usually in Math it means not as with inequality which means not equal and infinite which means not finite.

Inter- is another good prefix to teach as with words like intersection.

Icosahedron - a polyhedron made up of twenty equilateral triangles.

Icosidodecahedron - a polyhedron - one of the thirteen semi-regular Platonic solids. Formed by either cutting the dodecahedron one half of the way into each side or cutting the icosahedron one half of the way into each side.

Idempotent - the element x in some algebraic structure is called idempotent if x*x=x.

Identity - a number that when an operation is applied to a given number yields that given number. For multiplication, the identity is one and for addition the identity is zero.

Imaginary Axis - the y-axis of an Argand diagram.

Imaginary Number - a complex number of the form xi where x is real and i=sqrt(-1).

Imaginary Part - the imaginary part of a complex number x+iy where x and y are real is y.

Imperfect Power - a number which is not the product of equal factors.

Improper Fraction - a simple fraction whose value is equal to or greater than one, the numerator is greater than the denominator.

Incenter - the incenter of a triangle is the center of its inscribed circle.

Incircle - the circle inscribed in a given figure.

Indefinitely - an unspecified amount, having no exact limits.

Independent Events - two events A and B are independent if the probability that they happen at the same time is the product of the probabilities that each occurs individually.

Inequality - the statement that one quantity is less than (or greater than) another.

Infinite - a list of numbers that goes on forever and ever and never stops.

Infinitesimal - a variable that approaches 0 as a limit.

Infinity - greater than any fixed counting number, or extending forever. No matter how large a number one thinks, infinity is larger than that number. Infinity has no limits.

Inflection - a point of inflection of a plane curve is a point where the curve has a stationary tangent, at which the tangent is changing from rotating in one direction to rotating in the opposite direction.

Initiator - a line-segment or figure that begins as the beginning geometric shape for a fractal. The initiator is then replaced by the generator for the fractal.

Injection - a one-to-one mapping.

Input - the number or value that is entered, for example, into a function machine. The number that goes into the machine is the input.

Inscribed Angle - the angle formed by two chords of a curve that meet at the same point on the curve.

Integer - one of the member of this set: { ... , -3, -2, -1, 0, 1, 2, 3, 4, 5, ... }, numbers that express whole units.

Interest - a sum paid for the use of money.

Intersect - two figures are said to intersect if they meet or cross each other.

Intersection - the point where two lines cross.

Intersection of Sets - a set of elements that appears in both sets.

Involution - the process of raising a number to a given power.

Irrational Number - a number whose decimal part goes on forever and ever without repeating.

Irregular Fractals - complex fractals whose dimension is often difficult to determine and in some cases is unknown.

Isogonal Conjugate - isogonal lines of a triangle are cevians that are symmetric with respect to the angle bisector. Two points are isogonal conjugates if the corresponding lines to the vertices are isogonal.

Isometry - a length preserving map.

Isosceles tetrahedron - a tetrahedron in which each pair of opposite sides have the same length.

Isosceles Trapezoid - a trapezoid whose sides are the same length (congruent.)

Isosceles Triangle - a triangle with two equal sides.

Isotomic Conjugate - two points on the side of a triangle are isotomic if they are equidistant from the midpoint of that side. Two points inside a triangle are isotomic conjugates if the corresponding cevians through these points meet the opposite sides in isotomic points.

Item - the things or objects that are the subject of a bar graph.

Iteration - repeating a set of rules or steps over and over.

Thank you for visiting my Math words that start with I. Maybe you would like to have the whole collection as seen here.

## Free Printable Math Dictionary

You can print and keep these Math definitions as a glossary in your binder or a file folder. You can also download it to your tablet or bookmark this page. See the alphabetical links below for more online Math words.

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