Geometry Glossary - 0 

Oblate spheroid:

a "squished sphere"; its diameter is not constant; the earth is an oblate spheroid because its diameter when measured through the equator is longer than when measured from the North to South Pole

Oblique (when used in the name of a surface):

adjective that indicates the bases (for prisms and cylinders are parallel but not aligned, or the tip (for pyramids and cones) is not centered over the base

Obtuse Angle:

an angle whose measure is between 90° and 180°

Obtuse triangle:

a triangle with an obtuse angle

Octagon:

an eight-sided polygon

One-Dimensional:

existing on a line; having only length, but no width or depth

 

 

Opposite (sides and angle):

a side is opposite an angle of a triangle if and only if that side does not form the angle; an angle is opposite a side of a triangle if and only if the vertex of that angle is not an endpoint of the side 

Opposite Rays:

two rays that share only an endpoint and lie on the same line

Ordered Pair:

the "address" of a point on the coordinate plane; given by (x, y) where x is the direction and distance traveled parallel to the x-axis and y is the direction and distance traveled parallel to the y-axis

Origin:

the location of (0,0) on the coordinate plane

Orthocenter:

the point at which the altitudes of a triangle intersect; in the illustration shown below, Point P is the orthocenter

Overlapping figures:

 two or more figures that share sides, vertices and/or areas