Word  Definition  Examples  

D  
Data  Numbers collected for use in statistics and other forms of problem solving.  Data can be in lists, tables, graphs, charts, and many other ways.  
Decimals  A number written with place value instead of fractions or mixed numbers. Also used to approximate irrational numbers. See repeating decimals, truncated decimals , and nonrepeating decimals. 
2.25 = 2 ¼ 

Deductive reasoning  A method of reasoning logically from given facts, rules, definitions, or properties to a conclusion.  All oranges are fruits All fruits grow on trees Therefore, all oranges grow on trees 

Degree of a monomial  The sum of the exponents of all its variables  7x^{5}y^{2} is 5 + 2 or 7th degree  
Degree of a polynomial (single varable)  For a polynomial with only one variable, the highest degree of any of its terms  The biggest positive exponent  7x^{5} + 3x^{2}  8 is fifth degree  
Degree of a polynomial (multiple varables)  For a polynomial with more than one variable, the highest degree of any of its terms  7x^{5}y^{2} + 3x^{2}y^{2}  8 is 7th degree because the first term is degree 7, the second term is degree 4, and the number term is degree zero. 

Delta Δ δ  Greek letter frequently used to represent variables that change. Capital Δ usually represents a larger change (like slope) and small δ is a small change (used in physics and calculus).  
Dependent events  In probability, when the outcome of one event affects the outcome of a second event, the events are dependent  The probability of getting 2 heads in a row when you flip coins depends on if you get a head the first toss.  
Dependent variable  A variable that relies on the value of another variable  for y = x + 2, the value of y depends on the value of x  
Derivative  In Calculus, the formula for slope of a graph at any point on the graph. The process of finding the derivative is called differentiation  
Diameter  In a circle, any segment that contains the center of the circle and has both endpoints on the circle.  
Difference of two squares  A quadratic binomial of the form a^{2}  b^{2}, it
factors to (a + b)(a  b) 
Perfect square minus a perfect square  x^{2}  9 4x^{2}  25 

Dilation  A transformation in which a figure is made larger or smaller, but not moved.  
Direct variation  A linear function of the form y = kx, where k ≠ 0 
A straight line that passes through (0,0) with slope k  y = 5x y = 2x 

Discrete Data  Involves a count of data items  Things that can be counted  heart beats in a minute or daily temperature at noon 

Discontinuous Function  A graph of a function that has jumps, holes or breaks. It cannot be graphed without lifting your pencil.  
Discriminant  the term under the square root sign in the quadratic
formula: b^{2}  4ac


Distance Formula  Using the Phythagorean Theorem to find the distance between two points on a coordinant grid)  
Distributive property  For all real numbers a, b, and c: a(b + c) = ab + ac a(b  c) = ab  ac 
Multiply everything inside the parenthesis by the thing in front of the parentheses  5(x + 2) = 5x + 10 4(x  2) = 4x  8 

Divisible  a number that can be divided by a whole number with no remainder  See Divisibility Rules  
Domain  The set of all possible input values  the independent variable in a function. For functions in x and y, the possible x values are the domain.  For y = 2x + 6, the domain is all real numbers
For y = 7/x, the domain is all real numbers except 0 because you can't divide by zero 

Word  Definition  Examples  
E  
Element 


Elimination  Using addition or subtraction to eliminate one variable when solving a system of equations.  
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 + ∞  
Epsilon Ε ε  Greek letter sometimes used in math problems  
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 equal 

Equiangular triangle  A triangle where all the angles are congruent 
All angles equal 

Equilateral polygon  A polygon where all the sides are congruent  All sides equal  
Equilateral triangle  A triangle where all the sides are congruent 
All sides equal 

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)  y = 5x^{2} + 2  
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.  
Word  Definition  Examples  
F  
Factoring  Breaking a polynomial equation down into the product of several factors 


Factorial !  n! is the product of all the whole numbers from n down to 1  used in probability  3! = 3• 2 •
1 = 6 4! = 4 • 3• 2 • 1 = 24 

Factors  Whole numbers that are multiplied together to equal another number. See Divisibility Rules  2 and 5 are the factors of 10 because 10 = 2 • 5  
Factored Form  A polynomial written as the product of polynomials of lower degree  y = (x + 4)(x  3) is the factored form of y= x^{2} + x  12 

Favorable outcome  In a probability experiment, the possible results you want to happen  When flipping coins and you call heads, a favorable outcome is you getting heads.  
FOIL method  When multiplying two binomials, use the Distributive property repeatedly. F  first terms in each parentheses O  outside terms in each parentheses I  inside terms in each parentheses L  last terms in each parentheses 

Fraction  A ratio of two numbers representing part of a whole. A fraction is a real number. In Algebra, a fraction bar means to divide.  ½ means one half
it also means 1 divided by 2 

Frequency  The number of cycles per unit of time or the reciprocal of the period of the function.  
Foundation drawing  Drawing that shows the base of an object (its foundation) and the height of each part.  
Function  A relation that assigns exactly one value of the dependent variable to each value of the independent variable  Rule that matches one input to only one answer  y = x + 5 is a function if you pick x = 3 you get one answer, y = 8 

Function notation  A function written using the symbol f(x) in place of y  Another name for a function  a more formal name. Read it as "f of x"  f(x) = 2x + 3 y = 2x + 3 

Future value  In investment problems with interest, the future value is the value of the investment after interest has been earned. 
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