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A Glossary of Mathematical Terms - O


See Angle or Triangle.


An eight-sided polygon.

Odd number

An integer number that divided by 2 gives a remainder of 1.

One-to-one correspondence

A map where to not only to every element in the first set there corresponds one and only one element in the second set, but also vice-versa.


A specific process for combining quantities.

Opposites (Additive inverses)

Two numbers whose sum is 0.

Order of operations

The convention that detremines in which oder an expression is to be evaluated. A common mnemonic to help folks to remember the correct order for mathematical expressions is: Please excuse my dear aunt Sally. Parentheses, exponents, multiplication, division , addition, subtraction.

Ordered pair

A pair of objects in which the order is important.

Ordinal number

A number that describes order or position.


The second element in a coordinate pair.

first published on september 01 2003 - last updated on september 01 2003