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Absolute value  The distance from 0 to the graph of a number on the number line.

Acute angle  An angle with measure between 0° and 90°.

Acute triangle  A triangle with three acute angles.

Additive inverse Two integers that are opposite each other.  The sum of any number and its additive inverse is

zero.

Additive property of equality  If you add the same number to each side of an equation, the two sides remain equal.

Adjacent angles  Two angles with a common side and a common vertex, but with no common points in their

interiors.

Algebra A mathematical language that uses letters along with numbers. The letter (variable) stands for the   

unknown value.

Algebraic expression A combinations of variables, numbers and at least one operation.

Alternate interior angles One of two pairs of angles formed when a transversal intersects two lines.  In the

diagram, L I and L are one such pair, and L and L are the other.

Altitude A perpendicular segment from any point on the side opposite the base (of a parallelogram) to the line

containing the base

Angle A figure formed by two rays with a common endpoint.

Annual rate of interest  A percent of the principal figured on a yearly basis.

Approximate number A number used to express a measurement

Arc  A part of a circle.

Area  Amount of surface, measured in square units.

Arithmetic average The sum of the numbers in a set divided by the number of elements in the set.

Arithmetic sequence A sequence of numbers in which successive terms can be found by adding the same                   

number to the preceding term.

Associative property of addition For any numbers a, b and c, (a + b) + c = a + (b + c).

Associative property of multiplication For any numbers a, b and c, (a x b) x  c = a x (b x c).

Average The sum of two or more quantities divided by the number of quantities.