Title 
Description 

e, Base of Natural Logarithm 
A very important number, e is approximately 2.718281828459045. 

Eccentricity 
A parameter of conic sections. Eccentricity is itself rather eccentric, or out of the ordinary. 

Element 
Element has a lot of meanings. Each entry in a matrix is an Element. Each object in a set can be termed an Element. A constituent or piece of something bigger is also called an Element. 

Ellipse 
One of the conic sections, an Ellipse is a plane figure with welldefined properties that often include vertices and a major axis and a minor axis. 

Ellipsoid 
Think of a blimp (a zeppelin) or a football (American football). 

Empty Set 
The Empty Set is also called the Null Set. It is the set with nothing in it, and there is but one Null Set (or Empty Set). 

Epsilon 
The fifth letter of the Greek alphabet is Epsilon. 

Equal 
In the United States all men are created Equal, endowed by their Creator with certain unalienable rights that include life, liberty, and the pursuit of happiness. 

Equality 
A statement where two or more values are deemed to have an equal or identical value is a statement of Equality. 

Equation 
A statement of equality, or equal value, is termed an Equation. When we solve an Equation we solve for some entity or value that makes the statement true. 

Equiangular 
Having all angles of equal measure is to be Equiangular. Equilateral polygons are most often (but not necessarily) also equiangular; they are termed Regular Polygons. 

Equidistant 
Literally of the same distance to some reference point is the essence of Equidistant. 

Equilateral 
Polygons with all sides congruent are said to be Equilateral. Most Equilateral polygons are also equiangular (but not necessarily). Polygons that are both equilateral and equiangular are termed Regular Polygons. 

Equivalence 
When we establish Equivalence we set forth two or more equivalent or equal entities. 

Eta 
Eta is the seventh letter of the Greek alphabet. 

Euclidean Geometry 
The plane geometry we all study in school is a form of Euclidean Geometry, spiced with a few threedimensional figures for flavor. 

Euler's Formula (Complex) 
Euler's Formula for complex numbers expresses a complex number in trigonometric form. 

Euler's Formula (Polyhedra) 
V  E + F = 2. For any polyhedron, the number of vertices minus the number of edges plus the number of faces equals two. 

Evaluate 
When we Evaluate an expression we determine its value or the value of some entity within it to (typically) make the statement true. 

Even (integer) 
Even integers end with one of the following five digits: 0, 2, 4, 6, or 8. These digits are considered Even and the integers that end with them are also considered Even. When Even integers are divided by two the quotient is an integer. 

Even Function 
Even Functions are symmetrical about the yaxis, provided they are expressed as y = f(x). Even Functions adhere to the following: f(x) = f(x). 

Exact 
When a value is an Exact value it is either precise or equal to a given value or standard value. 

Exclusion 
Exclusion means to leave out or to not include some value, either from a set or for consideration into a set of values. 

Expansion By Cofactors 
Expansion By Cofactors is a process to evaluate matrix values such as determinants by taking a sum of values generated by the sum of cofactor products. 

Expected Value 
The Expected Value is, statistically, the real number or value that is most likely to occur for some event when examined as an average value. The Expected Value may not actually be an obtainable value; it is an average value. 

Explicit 
Ideas or notions directly expressed or understandable are considered Explicit. 

Exponent 
Usually written as a superscript, an Exponent is a number or entity to which some other value is raised, as a power. 

Exponential Decay 
When an established quantity loses value and decreases by some constant percentage over some constant period of time it is considered to experience Exponential Decay. 

Exponential Function 
An Exponential Function employs the independent variable as an exponent on a constant. If expressed as y = f(x), the Exponential Function will pass through (0,1). Such a function is the inverse to a logarithmic function. 

Exponential Growth 
When an established quantity gains value and increases by some constant percentage over some constant period of time it is considered to experience Exponential Growth. 

Expression 
A mathematical statement of almost any kind is considered an Expression. 

Exterior Angle 
An Exterior Angle is most commonly the angle formed between the extension of a side of a polygon and the adjoining side. 

Extraneous Solution 
Sometimes we perform mathematical manipulations and obtain solutions that do not make sense but nevertheless are obtained by following the rules of, say, algebra. Such solutions are termed Extraneous. Often they do not strictly satisfy the original conditions of the problem that was solved. 

Extreme Value Theorem 
On any continuous function graphed on a closed interval from a domain, we are guaranteed to have a maximum and a minimum value if the range of the function is not constant. 

Extremum 
The highest and lowest values for the output of a function are called Extremum, the singular form of plural extrema. 
