Title 
Description 

Oblique 
In one sense, at an angle or not perfectly horizontal or vertical. An Oblique triangle is any triangle that is not a right triangle.


Obtuse 
In common language Obtuse means obscure and confusing, obfuscatory. An Obtuse angle measures more than 90 degrees (and less than 180 degrees).


Octagon 
An eightsided polygon.


Octant 
As we have four quadrants in the rectangular plane, we have eight Octants in rectangular space. In three dimensions the three axes divide space into eight sections, each termed an Octant.


Odd 
In common language: strange or unusual. For integers, numbers ending with any of these digits: 1, 3, 5, 7, or 9.


Odd Function 
An Odd Function adheres to this property: f(x) = f(x). The standard sine function is an odd function.


Odds 
The likelihood or probability of an event or specific outcome is termed the Odds of the event occurring. Odds, or probabilities, are always represented with values between 0 and 1, or between zero and 100 percent (inclusively).


Omega 
The last, or 24th, letter of the Greek alphabet is Omega. Uppercase Omega is used for ohms, a unit of electrical resistance. Lowercase Omega is used for angular velocity, a speed of rotation.


Omicron 
The 15th letter of the Greek alphabet. We don't use it in math because it looks just like an "o" or a zero.


OneDimensional 
Linear, or along one line of direction. Informally, constrained to stay along a narrow line.


Open Interval 
A section of a line whose set does not include the endpoints is considered an Open Interval.


Operation 
The processes of addition, subtraction, multiplication, and division are each termed an Operation. So, too, is raising a value to a exponent.


Opposite 
Many meanings are found for Opposite, including having direction 180 degrees from an original direction, or having the negative sign of a previous sign. Opposite real values have identical absolute values.


Order of Operations 
We have a hierarchy of Order to Operations in the language of mathematics. We do multiplication before we do addition, and we also work lefttoright. We work first inside of expressions within parentheses, then outward.


Order, Matrix 
The Order of a Matrix is its size, expressed as "rows by columns." 

Order, Polynomial 
The Order of a Polynomial relates to the highest power of variables in a term, typically the Order of the leading term of the Polynomial.


Ordered Pair 
Two coordinates are required to label a point in a plane, typically (x, y).


Ordered Triple 
Three coordinates are required to label a point in space, typically (x, y, z).


Ordinal Number 
Ordinal Numbers are ordinary numbers, or the sequential references of order as first, second, third, and so on.


Ordinary Differential Equation 
A Differential Equation with no partial derivatives is considered an Ordinary Differential Equation.


Ordinate 
In Cartesian or rectangular coordinates, the yaxis, or the coordinate from the yaxis; the second coordinate in an ordered pair.


Origin 
In one dimension: (0). In two dimensions: (0,0). In three dimensions: (0, 0, 0).


Orthocenter 
The Orthocenter of a triangle is the point of concurrence of the altitudes of the triangle.


Orthogonal 
Most generally Orthogonal means perpendicular to a plane.


Outcome 
A specific event is often termed an Outcome.


Outlier 
When plotting data points, as in a scatterplot, if a single data point is far removed from the neighborhood of the other data points, such a farremoved data point is called an Outlier.


Oval 
In common language, any elliptical shape or notquite round "circular" shape is called an Oval. Mathematically, an ellipse is not an Oval.

