Word  Definition  Examples  

Element 
Visit Math is Fun for a great explaination of sets. 

Elimination  Using addition or subtraction to eliminate one variable when solving a system of equations.
Purple Math has a simple explaination, and Math Planet shows a more difficult explaination. 

End behavior  The way a graph of an equation behaves at the far left and right ends as
the input variable goes to positive or negative infinity + ∞
For the cubic equation graphed here, at the left end (very negative) the graph goes down to negative infinity. The right side (very big positive) the graph goes up to positive infinity. 

Epsilon Ε ε  Greek letter used
in math problems. In Calculus, the small epsilon is used to represent very small positive numbers. 

Equation  Two expressions that are equal.  Uses the = sign to show the relationship that two
things are equal to each other. Each side of the equation is an expression. 
x + 2 = 7
4x^{2} + 2x = 7 
Equiangular polygon  A polygon where all the angles are congruent
All angles are equal, but the size of the angles depends on the number of sides in the polygon 

Equiangular triangle  A triangle where all the angles are congruent All angles are equal and, because it is a triangle, they must equal 60 degrees. 

Equilateral polygon  A polygon where all the sides are congruent. All sides are the same length (equal in length). 

Equilateral triangle  A triangle where all the sides are congruent  all sides are equal.
Note: an equilateral triangle is also equiangular! 

Euler Line  In geometry, the centroid, circumcenter and orthocenter of any triangle always lie on a straight line, called the Euler line. Click here to see an animated example of the Euler line.  
Even function  A function graph whose axis
of symmetry is the yaxis. f(x) = f(x) 

Even number  Any number that can be divided by 2 with no remainder. In Algebra, 2n can represent any even number.  
Event  In probability, any group of outcomes  The possible results  When rolling one dice, the outcomes are 1, 2, 3, 4, 5, or 6 
Exact number  Am number that is the result of counting or the results from a theoretical calculation.  Measurements are not exact numbers.  
Experimental data  In statistics, data that collected from an experiment set up specifically to answer a question.  
Experimental probability  In probability, the ratio of the number of times an event happens to the number of times the experiment is done  Results from doing an experiment  P(event) = times it happened ÷ times you tried 
Exponent  A raised number that represents repeated multiplication of a factor  3^{4} = 3 • 3 • 3 • 3  
Exponential decay  An equation used to calculate how things get smaller over time  used for radioative decay and age dating.  y = C(1  r)^{t} where y is the final amount, C is the original amount, r is the rate of change, and t is time. 

Exponential function  An equation of the form y = b^{x} where there is a variable as an exponent. Exponential functions are the inverse of logarithms  
Exponential growth  An equation used to calculate how things increase over time  used for growth of bacteria and other populations.  y = C(1 + r)^{t} where y is the final amount, C is the original amount, r is the rate of change, and t is time. 

Expression  Any combination of values and operations (no = sign)  4x^{2} + 2x  
Exterior angle  In a polygon, the angle formed by a side and an extension of a side.  
Extraneous Solution  A number that comes when you solve an equation, but it doesn't work in the original equation. Frequently occurs in equations that have a variable under a square root sign. 
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