diopter

[dahy-op-ter]

noun

Optics. a unit of measure of the refractive power of a lens, having the dimension of the reciprocal of length and a unit equal to the reciprocal of one meter. Abbreviation: D
an instrument, invented by Hipparchus, to measure the apparent diameter of the sun or moon or to estimate the size or elevation of distant objects.

Also especially British, di·op·tre.

Origin of diopter

1585–95; < Latin dioptra < Greek: instrument for measuring height or levels, equivalent to di- di-³ + op- (for ópsesthai to see) + -tra noun suffix of means

Related formsdi·op·tral, adjective

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for diopter

Historical Examples of diopter

The unit of power employed by spectacle-makers is termed the diopter or dioptric (see Spectacles).
Encyclopaedia Britannica, 11th Edition, Volume 16, Slice 4
Various
Diopter, the unit in terms of which the power of a lens or curved mirror can be expressed.
The New Gresham Encyclopedia
Various

diopter in Medicine

diopter

[dī-ŏp′tər]

A unit of measurement of the refractive power of lenses equal to the reciprocal of the focal length measured in meters.