Word  Definition  Examples  

Identity  An equation that is true for every value of the variable  Always true  x + 1 = 1 + x  
Identity Property of Addition  The sum of any number and zero is that number  Anything + 0 = Itself  a + 0 = a  
Identity Property of Multiplication  The product of any number and one is that number  Anything x 1 = Itself  a • 1 = a  
Image  The position of a figure after a transformation.  
Imaginary Number  A number of the form a + bi, where i is the square root of 1 and i^{2} = 1  √(4) = 2i  
Impossible Event  In probability, an event that never happens  Getting 4¼ when you roll one dice is impossible  
Improper fraction  A fraction where the numerator is larger than the denominator. In arithmetic, you are trained to change these to a mixed number. In Algebra, you should leave it alone. 


Incenter  The point in a triangle where the angle bisectors of the triangle intersect. Click here for an animated example of the incenter.  
Independent Events  In probability, when the outcome of one event does not affect the outcome of a second event, the events are independent  
Independent Variable  A variable that does not depend on another variable  The input variable  For y = x + 3 x is independent 

Inductive Reasoning  A method used to reach conclusions based on an observed pattern.  For the pattern 2, 4, 6, 8 you can induce that since they are all even numbers, the next number must be 10  
Inequality  One expression that is not equal to another  x > 7 means x is greater than 7 2 < x means negative 2 is less than x 4 < x means x is 4 or bigger 

Infinity  The concept of something that never ends  infinity is not a number  ∞  
Integer  The whole numbers and their opposites  ...  3, 2, 1, 0, 1, 2, 3, ...  
Integral ∫  In Calculus, the area between the graph of a line and the xaxis. The process of finding the integral is called integration  
Intersect  Lines intersect when they cross. The point where they cross is called the intersection.  
Interval  A portion of the real number line that may or may not include the end points. The ends of the interval are called the boundaries.  
Interval notation  A short way to define an interval. Brackets [ or ] are used
if the end point is part of the interval. Parentheses ( or ) means the
end point is not included in the interval. For ∞ and  ∞, always use parentheses. 
[3, 5) means 3 < x < 5 

Inverse Operation  Operations that undo each other  they are opposite operations  addition and subtraction are inverses multiplication and division are inverses squares and square roots are inverses 

Inverse Variation  A function that can be written in the form xy = k or y = k/x  As one variable gets bigger, the other gets smaller  
Irrational number  A number that cannot be written as a fraction.  A decimal that does not truncate (end) or repeat.  π = 3.14159... √7 = 2.6457... 

Isometric drawing  The drawing of a threedimensional object that shows the corners.  
Isosceles trapezoid  A trapezoid whose nonparallel sides are congruent. The top and bottom are parallel, the sides are the same size, and the diagonals are equal. 

Isosceles triangle  A triangle where at least two sides are congruent  Two or more sides equal 
Comments, questions, or you just need some help? Send an email to Mrs. Shearer
Last Updated: 6/26/2014
© K. A. Shearer 20052014
Buttons created at ButtonGenerator.com.