Math Vocabulary - A


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 multi-year 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.
The red line is the transversal - the line that cuts.

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 ∠
When naming an angle, start with a point one one side, put the vert5x in the middle, and finish with a point on the other side.

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 x-axis

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
2 x (6 x 5) = 2 x 30 = 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 = 2x2 + x - 1
the axis of symmetry is the line x = -b/2a = -1/(2*2) = - 1/4 or -0.25

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Last Updated: 06/14/2014
K. A. Shearer 2005-2014
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