obtuse angle

An angle whose measure is greater than 90 degrees.

optical illusion

A drawing or object that appears to have an effect that it does not really have, such as when a flat painting seems to have three-dimensional depth.

origin

In the Cartesian coordinate plane, the origin is the point at which the horizontal and vertical axes intersect, at zero (0,0).

outcome

Any one of the possible results of an experiment.

outcome space

The outcome space is the set of all possible outcomes of a given experiment.

outlier

A data point (or points) that lie far outside most of the rest of the points in the data set.

output

The number or value that comes out from a process. For example, in a function machine, a number goes in, something is done to it, and the resulting number is the output.