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dioptre

Pronunciation: /dʌɪˈɒptə/
(US diopter)
Definition of dioptre

noun

  • a unit of refractive power, which is equal to the reciprocal of the focal length (in metres) of a given lens: vision corrected to within one dioptre of perfect sight

Origin:

late 16th century (originally as diopter, denoting an alidade): from French, from Latin dioptra, from Greek, from di- 'through' + optos 'visible'. The term was used in the early 17th century to denote an ancient form of theodolite; the current sense dates from the late 19th century

dioptre in other Oxford dictionaries

Definition of dioptre in the US English dictionary
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