Math Glossary: o
| Oblique Angle | An angle which is not a right angle, can be obtuse or acute. |
| Obtuse Angle | One that is greater than 90 degrees. |
| Obtuse Triangle | A triangle with one angle greater than 90 degrees, and therefore the other two angles must be acute. |
| Octagon | A polygon with 8 sides and 8 angles. |
| Order of Operations | The specific order in which mathematical operations are to be performed. |