Abscissa

This is the X coordinate on a Cartesian graph. The Cartesian system is the one that looks like a grid full of squares.

Absolute Value

The absolute value is the number's distance from zero on the number line. This action ignores the + or  sign of a number. x is the graphic used to describe the action of absolute value. Example: 5 = 5 or 5 = 5.

Accuracy

Accuracy is how close a numerical measure is to its actual value.

Acute Angle

An acute angle is an angle that has a value greater than 0 degrees but less than 90 degrees (90º). We're sure it's adorable, too.

Acute Triangle

An acute triangle is one where all three angles are acute. Acute angles have values less than 90 degrees.

Add

To combine two or more quantities to find one quantity called a total or sum.

Addend

An addend is any number that is being added. Example: 3 + 5 + 1 = 9. 3, 5, and 1 are addends.

Addition

Addition is the mathematical operation of combining two or more numbers into a sum.

Addition Fact

The addition of two singledigit addends producing sums to 18.

Addition Sentence

An addition sentence is an equation that shows the sum of two or more numbers. Example: 12 + 6 = 18.

Additive Inverse

A number that when added to a given number results in a sum of zero; the opposite of a number.

Adjacent

Adjacent things are next to each other.

Adjacent Angles

Two angles in a plane that share a common side and share a common vertex but have no interior points in common (do not overlap).

After

Something that is after is behind in place, subsequent to in time or order.

Algebra

Algebra is the branch of mathematics that uses letters, symbols, and/or characters to represent numbers and express mathematical relationships. Those symbols are called <b>variables</b>.

Algebraic

Making use of or referring to concepts or methods of algebra.

Algebraic Expression

An algebraic expression is a mathematical phrase that is written using one or more variables and constants, but which does not contain a relation symbol (). Example: 5y + 8.

Algebraic Inequality

An algebraic statement that is written using one or more variables and constants that shows a greater than or less than relationship. Example: 2x + 8 > 24.

Algebraic Pattern

An algebraic pattern is a set of numbers and/or variables in a specific order that form a pattern.

Algebraic Relationship

To express the relationship between two or more numbers using an algebraic expression.The algebraic relationship which represents 2, 4, 6, 8... is2n (where n = 1, 2, 3, ...) and the algebraic relationship which represents 4, 7, 10, 13, ... is 3n + 1 (where n = 1, 2, 3, ...).

Algebraic Solution

An algebraic solution is the process of solving a mathematical problem using the principles of algebra.

Algebraic Term

An algebraic expression, called a monomial, involving only multiplication between constants and at least one variable. Example: 3xy.

Algebraically

Representing a mathematical situation using algebra.

Algorithm

An established and welldefined stepbystep method used to achieve a desired mathematical result. Example: The addition algorithm for the sum of two twodigit numbers where carrying is required.  The procedure used in long division.

Alternate Exterior Angles

A pair of angles on the outer sides of two lines intersected by a transversal, but on opposite sides of the transversal.

Alternate Interior Angles

A pair of angles on the inner sides of two lines intersected by a transversal, but on opposite sides of the transversal.

Altitude of a Cone or Pyramid

A line segment (or its length) drawn from the vertex of the cone perpendicular to the plane containing the base.

Altitude of a Cylinder or Prism

A line segment (or its length) drawn from any point on one base perpendicular to the plane containing the other base.

Altitude of a Triangle or Quadrilateral

A line segment (or its length) drawn from a vertex perpendicular to the line containing the opposite side.

Amount

The sum, the whole, or aggregate of two or more quantities.

Analog Clock

A clock with a minute hand and an hour hand.

Angle

A geometric figure formed by two noncollinear rays that have a common endpoint.

Angle Bisector

A segment or ray that divides an angle into two congruent angles.

Angle Pairs

Pairs of angles with special relationships (e.g., supplementary angles, complementary angles, vertical angles, alternate interior angles, alternate exterior angles, corresponding angles, adjacent angles).

Ante Meridiem

a.m. Before noon; the time between 12 midnight and 12 noon; 12 midnight is 12 a.m. After noon is prime meridiem (p.m.).

Apply

To use a theorem or concept to solve an algebraic, numeric, or geometric problem.

Approximation

A mathematical quantity that estimates a desired quantity.

Arbitrary Unit

A unitor measure that is not part of the standardized metric or US Customary systems. For example, using one’s own shoe size to measure the length of a door opening or saying that the area of an exhibition hall floor is "about the size of two football fields."

Arc

Part of a curve between any two of its points.(See major and minor arc)

Area

The measure, in square units, of the inside of a plane figure. The area must be a measure of a closed region or figure.

Argument

The communication, in verbal or written form, of the reasoning process that leads to a valid conclusion; a valid argument is the result of the conjecture/reasoning process.

Arithmetic

The simplest part of mathematics. When you study arithmetic you learn about addition, subtraction, multiplication, and division (called operations). Some more advanced ideas are included in arithmetic, but those are the big four. They are the foundation for all higher mathematics.

Arithmetic Expression

(See numeric expression)

Arithmetic Sequence

A sequence of elements, such that the difference of any two successive terms is a constant. The formula to describe the sequence is a_{i+1}  a_{i} = k. Example: {2,5,8,11,14,...} has the common difference of 3.

Arithmetically

Computing using numbers.

Array

An arrangement of objects or numbers, usually in rows and/or columns.

Ascending Order

Arranged in order from least to greatest or smallest to largest.

Associative Property

A property of real numbers that states that the sum or product of a set of numbers is the same. It doesn't matter how the numbers are grouped, the sum is the same. The associative property also works for an equation when all numbers are multiplied. Example: Addition: 2 + (3.5 + 1.3) = (2 + 3.5) + 1.3

Asymptotes

Straight lines that have the property of becoming and staying arbitrarily close to the curve as the distance from the origin increases to infinity. For example, the x axis is the only asymptote to the graph of sin( x)/x.

Attribute

A characteristic of an object, such as color, shape, size, etc. That characteristic can also identify the object as part of a larger group.

Average

The average is the total of all pieces added up and divided by the number of pieces. Scientists use the word average to explain entire systems. Even though there are a few pieces with very high numbers and a few with very low, those two "average" 
Axes

The horizontal and vertical lines dividing a coordinate plane into four quadrants. 
Axiom

An axiom is a mathematical rule. This basic assumption about a system allows theorems to be developed. For example, the system could be the points and lines in the plane. Then an axiom would be that given any two distinct points in the plane, there is a unique line through them. 