# Online Math Dictionary: E

Easy to understand math definitions for K-Algebra mathematics
Just scroll down or click on the word you want and I'll scroll down for you!

 edge ellipse ellipsoid empty set equality equation equidistant equilateral triangle estimate even number expanded notation exponent exponential exterior angle

 EdgeThe edges of a polygon are the outside boundaries.  In thesquare on the right, you can see four  edges.   In a polyhedron, like the dodecahedron on the right, an edge is where two faces meet.  The edges are the yellow lines.

 EllipseThere's an easy definition for an ellipse and a harder algebra definition.  Here's the easy one:   An ellipse is a stretched out circle.For the algebra definition, check out.Coolmath Algebra Ellipses

 EllipsoidAn ellipsoid is a three dimensional ellipse.  Imagine putting a line through the longest part of an ellipse and spinning it.  This would give you an ellipsoid.

 Empty SetAn empty set is the same as a "null set."  An empty set is a set with no members (or elements.)  The symbol for the empty set is on the right.  It can also be written as an empty set of set brackets:                                        {   }Putting the empty set symbol inside the set brackets is a bad thing...  But, is a common mistake, so don't do it!

Equality
A math statement showing that two things are equal.
Example:   3 + 2 = 5

Equation
A math statement showing that two things are equal.  (Same thing as an equality.)
Example:   3 + 2 = 5

Equidistant
Equidistant just means "the same distance."

 Equilateral TriangleAn equilateral triangle is a triangle whose sides are all the same length (congruent). For more info, check out Properties of Triangles, Triangle Notations and Types of Triangles

Estimate
When you estimate the answer to a problem it means that you give a pretty good guess at what the answer will be.
Example:   199 x 302 =      Well, that's close to 200 x 300 which is 60,000. (I can do that in my head).   So, my estimate for the answer is 60,000.  The real answer is 60,098.

Even Number
An even number is a number that is cleanly divisible by 2.  (When I say "cleanly divisible" I mean that there is noremainder.)
Example:  2, 4, 6, 8, ...

Expanded Notation
Expanded notation is when you write a number out to show all the place values.
Example:   5682 = ( 5 x 1000 ) + ( 6 100 ) + ( 8 10 )  + ( 2 1 )