__R__

**Radical
** An expression such as
square root.*.*

**Radius
** A line segment joining any
point on a circle or sphere to the center.
Also the length of that segment.

**Random
variable ** A variable whose
value is determined by the outcome of a random experiment.

**Range
** The difference between
the greatest and the least numbers in a set of data.

**Rate ** A
ratio that compares quantities of different kinds of units.

**Ratio
** 0 An indicated quotient of two
numbers.

**Ray ** A
part of a line with one endpoint.

**Real
number ** Any number that is
either a rational number or an irrational number.

**Reciprocals
** Two numbers whose product
is 1.

**Rectangle
** A quadrilateral with four right
angles.

**Rectangular
prism **A prism of which all the faces are rectangles

**Regular
polygon ** A polygon in
which all sides are congruent and all angles are congruent.

**Reflection:
**A mirror image of a figure across a line of symmetry.

**Relation
** A set of ordered pairs.

**Relatively
prime numbers **Two or more numbers that have no other common factor but 1.

**Remainder
**The last difference obtained in the division process

**Repeating
decimal **A decimal numeral in which a digit or series of digits other than
zero repeat forever in the

same
pattern

**Rhombus
** A parallelogram in which all
sides are congruent.

**Right
angle ** An angle with
measure 90°.

**Right
prism **A solid with bases that are congruent polygons which lie in parallel
planes and are perpendicular

to
the lateral faces (sides) of the prism

**Right
triangle ** A triangle with a
right angle.

**Rigid
motions ** Motions such as
rotation, translation, and reflection, used to move a figure to a new position
without

**Roster
method **Defining or listing a set by naming the set with a capital letter,
and naming the elements within

a
pair of braces

**Rounding
**Writing a number to a certain approximation