Word  Definition  Examples  

Absolute Value  Distance of a number from zero on a number line. Since distance is always positive, the absolute value of any number must be positive. Caution: be careful when taking the absolute value of a variable, since you may have several possible correct solutions. 

Acute angle  An angle that measures between 0 and 90 degrees
0° < x < 90° 

Acute triangle  All angles in the triangle are acute  
Additive Identity  0  zero When you add zero to anything it does not change the value. When you subtract zero from anything you do not change the val;ue. 
0 is the additive identity in algebra because a + 0 = 0 + a = a 

Additive Inverse  A number and its opposite  When you add them they equal zero.  5 and 5 are inverses because 5 + (5) = 0 
Adjacent angles  Two coplanar angles with a common side, a common vertex,
and no common interior points Common means shared or the same, so adjacent angles share one side and the vertex. 

Adjacent arcs  Two arcs in the same circle that have exactly one point in common. Adjacent means "touching", so the two curves are touching, but do not overlap. 

Algebra  The study of equations using variables. At many schools, the study of algebra
is broken into Algebra 1 and
Algebra 2. For many schools using Common Core Standards, these are included in a multiyear integrated or connected math series. 

Algebraic expression  A collection of letters (variables) and real numbers (constants) combined using the operations of addition, subtraction, multiplication, division, and exponents.  
Alpha Α α  Greek letter  a small alpha is frequently used in geometry and trigonometry to represent angles  
Alternate exterior angles  When two lines are cut by a transversal, the alternate exterior angles
are on opposite sides of the transversal and the outside of the two lines
In this picture, angles 1 and 8 are alternate exterios angles. Angles 2 and 7 are also alternate exterior angles.


Altitude  The height of an object measured perpendicular (90 degrees) from the bottom to the top  
Amplitude of a periodic function  Half the difference between the maximum and minimum values of the function  
Angle  The shape formed by two rays (called sides of the angle) with the same
endpoint (called the vertex of the angle).
In geometry an angle can be
defined by the vertex or by the rays and vertex. The symbol for angle is ∠

∠M or ∠ LMN  
Angle bisector  A ray that divides an angle into two congruent (equal) angles  
Angle in standard position  An angle that has its vertex at the origin and its initial
side along the positive xaxis
The origin is the (0,0) point where the x and y axis cross. 

Angle of Depression  An angle from the horizontal looking down to a line of sight  The angle between the viewer and something below them  
Angle of Elevation  An angle from the horizontal looking up to a line of sight  The angle between the ground and something above the ground  
Apothem  A line segment that is drawn from the center of a regular polygon perpendicular to one
side of the polygon. A regular polygon is a shape where all sides and all angles are equal. 

Arc  Part of a circle  Exactly half the circle is called a semicircle.
Less than half is a minor arc and more than half is a major arc. 

Arithmetic Mean  The arithmetic mean of numbers is the sum of the numbers divided by how many numbers you added  also called the average  The mean of 3 and 8 is 5.5 Because you add 3 and 8 to get 11. Then, because you have two numbers you divide that answer by two  11 divided by 2 is 11. 

Arithmetic Sequence  A numerical pattern where the difference between consecutive terms is a constant Difference means you subtract 
The arithmetic sequence 1, 4, 7, 10, 13, ... has a common
difference of 3 because 4  1 = 3, and 7  4 = 3, and 10  7 = 3 and so on. In a sequence, the ... at the end means the pattern keeps going forever. 

Associative Property  Changing the grouping of addends or factors does not change the sum or product. Grouping doesn't matter when adding or multiplying  (2 + 3) + 4 = 5 + 4 = 9 2 + (3 + 4) = 2 + 7 = 9 (2 x 6) x 5 = 12 x 5 = 60 

Asymptote  A line the graph of a function gets close to but never gets exactly there. In the example, this shape is called a hyperbola. 

Axis of Symmetry  The line about which you can reflect a graph onto itself also the vertical line containing the vertex of a parabola. When you fold a graph on the axis of symmetry, both sides match. For the parabola, y = 2x^{2} + x  1 
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