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A unit of measurement of the refractive power of lenses equal to the reciprocal of the focal length measured in meters.
[Obsolete diopter, an instrument for measuring angles, from Latin dioptra, from Greek dioptrā : dia-, dia- + optos, visible; see okw- in Indo-European roots.]
di·op′tral (-trəl) adj.
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. Abbr.: DAlso, esp. Brit.,di•op′tre.
[1585–95; < Latin dioptra < Greek: instrument for measuring height or levels =di- di-3 + op- (for ópsesthai to see) + -tra n. suffix of means]
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|Noun||1.||diopter - a unit of measurement of the refractive power of a lens which is equal to the reciprocal of the focal length measured in meters; used by oculists|