The optical element which receives light from the object and forms the first or primary image in telescopes, microscopes and other optical systems.
Objective Tinnitus
This refers to abnormal or pathological sounds originating within the body, in the region of the ear, which are audible to others than the subject.
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.
Observations refer to repeated values of a data variable. The rows of a column represent the observations.
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.