Ob
- Objective
- The optical element which receives light from the object and forms the first or primary image in telescopes, microscopes and other optical systems.
- Oblate Spheroid
- An ellipsoid produced by rotating an ellipse through 360° about its minor axis.
- Obligate Anaerobes
- An organism that dies when exposed to oxygen.
- Oblique Angle
- An angle that is not a right angle.
- Oblique Coordinates
- A coordinate system in which the axes are not perpendicular.
- Oblique Triangle
- A triangle that is not a right triangle.
- Observation
- Observations refer to repeated values of a data variable. The rows of a column represent the observations.
- Obsidian
- A black or dark-coloured volcanic glass, usually composed of rhyolite.
- Obtuse Angle
- An angle larger than 90° but smaller than 180°.
- Obtuse Triangle
- A triangle that contains an obtuse angle.