Definition of dioptre noun from the Oxford Advanced Learner's Dictionary



(especially US English diopter) noun
BrE BrE//daɪˈɒptə(r)//
; NAmE NAmE//daɪˈɑːptər//
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a unit for measuring the power of a lens to refract light (= make it change direction) Word Originlate 16th cent. (originally as diopter): from French, from Latin dioptra, from Greek, from di- ‘through’ + optos ‘visible’. The term was used in the early 17th cent. to denote an ancient form of theodolite; the current sense dates from the late 19th cent.