# Math Vocabulary

Word Definition Examples
P   Parabola The curved shape you get when you graph a quadratic function
Parallel lines Lines that are always the same distance apart, they never cross. Lines that have the same slope y = 3x + 1 and y = 3x - 5 are parallel because they both have slope = 3
Parallelogram A quadrilateral where the opposite sides are parallel Rectangles, squares, and diamonds are parallelograms
Pascal's Triangle A pattern for finding the coefficients of the terms in a binomial expansion. It is also used in probability.

1
1   1
1   2   1
1   3   3   1

Percent % A portion of 100 .65 = 65/100 = 65%
Perfect squares Numbers whose square roots are rational numbers 1, 4, 9, 16, 25, 36, and 49 are perfect squares
Ľ is also a perfect square
Period of a function The horizontal length of one cycle of a periodic function. Most trigonometric functions have a period that is related to 2p radians or 360° See Trigonometry
Perpendicular bisector A line, segment, or ray that is perpendicular to the original segment at its midpoint Perpendicular lines Lines that cross at right angles. The product of the slopes is -1. y = 2x + 1 and y = -˝x - 5 are perpendicular because 2 • (-˝) = -1
Pi Π π Most frequently used Greek letter, it represents the ratio of diameter to circumference in math problems about circles. It also represents an angle measure in radians equal to 180°
Plane A flat surface that extends forever in all directions. Planes have no thickness. Usually drawn as a shaded parallelogram.
Point A location in space that has no size. Any point can be uniquely identified by a set of coordinates (x, y).
Point of intersection The point where two lines intersect or cross. If the lines are represented on a coordinate grid, the coordinates for the point of intersection can be read from the graph.
Polygon A closed plane figure with at least three sides A triangle is a 3-sided polygon
Polynomial A statement with one or more terms - poly means many 5x2, -72, and 3x2 + 2x - 1 are polynomials
Position vector A vector with its initial point at the origin
Positive angle An angle formed by counter clockwise rotation about its endpoint.
Postulate An accepted statement of fact that can be used to prove theorems "Two points define exactly one straight line" is a postulate
Power The exponent x5 is x to the fifth power
Probability The chance that something will happen. For example, the probability that you will get a head when you flip one coin is 1 chance out of 2 or 1/2.
Properties In geometry, statements that are accepted as true and are used with deductive reasoning to prove other statements.
Properties of equality For all real numbers, a, b, and c:
Addition: If a = b, then a + c = b + c
Subtraction: If a = b, then a - c = b - c
Multiplication: If a = b, then a • c = b • c
Division: If a = b, and c ≠ 0, then a/c = b/c
Proportion A statement that two ratios are equal - two fractions that are equal
 1 = 3 5 15
Protractor A device used to measure the size of an angle in degrees.
Pure imaginary number A complex number a + bi, where a = 0 and b is not zero
Pythagorean theorem In a right triangle, the sum of the squares of the lengths of the two sides (legs a and b) is equal to the square of the length of the hypotenuse (c). Click here to see an animated graphical "proof" of the theorem.

a2 + b2 = c2

Word Definition Examples
Q    Quadrants The coordinate x-y plane is divided into four quadrants by the x axis and y axis. Quad means four. The quadrants are usually labeled with roman numerals, starting at the top right and numbering counter-clockwise.
 II I III IV
Quadratic equation An equation written in the form ax2 + bx + c = 0 where a, b, and c are real numbers and a 0 The largest exponent is 2 2x2 - 3x + 4 = 0
 if ax2 + bx + c = 0 and a ≠ 0, then x = -b ± √(b2 - 4ac) 2a
Quadratic function A function with an equation written in the form
y = ax2 + bx + c where a 0
Graph as a parabola - the largest exponent is 2 y = 2x2 - 3x + 4
Quadrilateral A geometric figure with four sides and four angles A rectangle is quadrilateral
Word Definition Examples
R    Radian A unit of measure for angles, used in trigonometry, calculus, and advanced math and physics.

Radical A square root sign or any other root, like a cube root or fourth root

√5

Radius In a circle, any segment that has one endpoint at the center of the circle and the other endpoint on the circle
Range The set of all possible output values of a function - the dependant variable. For functions in x and y, the possible y values are the range. Possible answers for y = |x| the range is all positive numbers and 0
Ratio Comparing two numbers by division A fraction ľ and 3:4
Rational expression An expression with fractions, especially when there is a variable in the denominator. The variable can not make the denominator equal to zero
Rational number A number that can be written as a fraction. This includes whole numbers, fractions, and decimals that truncate (end) or repeat. ˝, ľ, 2.5 and -3 are rational
Rationalize the denominator Make the denominator of a fraction a rational number without changing the value of the expression Get rid of any signs in the denominator
 3 = 3√5 √5 5
Ray The part of a line consisting of one endpoint and all the points extending forever in one direction
Real number A number that is either rational or irrational All numbers except imaginary numbers √5, ˝, ľ, 2.5, 0, π and -3 are real numbers
Reciprocal Multiplicative inverse of a nonzero number. The product of a number and its reciprocal is 1. To get the reciprocal;

Flip it!

 2 and 3 3 2
are reciprocals because
 2 • 3 = 1 3 2
Rectangle A parallelogram with four right angles
Regular polygon A polygon that is both equilateral and equiangular.
Relation Any set of ordered pairs
Relationship symbols Symbols that compare two numbers. This includes the equal sign.

5 < 7
-2 > -8

Remote interior angles For each exterior angle of a triangle, the two non-adjacent angles Repeating decimal A decimal expression of a fraction, where the digits repeat. The repeating part is written with a bar over it to represent that the pattern repeats infinitely. 1/3 = 0.33333...
Rise The vertical change between two points on a graph. The slope of a line is the rise divided by the run. Comments, questions, or you just need some help? Send an e-mail to Mrs. Shearer 