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diopter

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diopter

Main Entry:: di·op·ter
Pronunciation:: \dī-ˈäp-tər, ˈdī-ˌäp-\
Function:: noun
Etymology:: diopter (an optical instrument), from Middle French dioptre, from Latin dioptra, from Greek, from dia- + opsesthai to be going to see — more at optic
Date:: circa 1864

: a unit of measurement of the refractive power of lenses equal to the reciprocal of the focal length in meters

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