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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.