__E__

**Edge
**(of polyhedron) A line segment formed by the intersection of two faces of a
polyhedron

**Edge
**(of prism) A line segment formed by the intersection of two faces of a prism

**Element
**A member of a set

**Empty
set **The set with no elements, represented by 0. (Some mathematicians also
use f I to represent the empty set.)

**Endpoint
** The point at the end of a line segment or ray.

**Equality
**(of fractions) Two fractions,
__a__

**Equation
** A mathematical sentence with an equals sign to indicate
that two expressions name the same number.

**Equiangular**
A polygon with equal angles. (Regular polygon).

**Equilateral
triangle ** A triangle in which
all sides are congruent.

**Equivalent
equations ** Equations that
have the same solution.

**Equivalent
fractions** Fractions that name the same number.

**Equivalent
inequalities ** Inequalities
that have the same solutions.

**Estimate
**A guess made as the answer to a problem by using numbers which are close in
value to the numbers

used
in the problem)

**Evaluate
an expression ** To replace
a variable in an expression with one of its values and then complete the

indicated
arithmetic.

**Event**
A specific outcome or type of outcome.

**Exact
number **The number used to express a count of objects (308)

**Expanded
form ** The method of
representing a number as the sum of products of each digit and powers of 0.

**Expanded
notation **Writing a number as an indicated sum of face values times place
values (13)

**Expected
value** The average value that one would expect to get over many attempts.

**Experimental
probability** An estimated probability based on the relative frequency of
positive outcomes

occurring
during an experiment.

**Exponent**
A number indicating how many times the base is used as a factor. In 5^{4},
the exponent is 4.

**Exterior
angle** If the a side of a polygon is extended, an exterior angle is formed.

**Extremes
of a proportion ** 0 The first and
last terms of a proportion.