diopter

noun di·op·ter \ dī-ˈäp-tər , ˈdī-ˌäp- \

Definition of diopter

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

Recent Examples of diopter from the Web

Monoyer invented the diopter, a unit of measurement that determines the distance someone must be from a text to read it.

— brett molina, USA TODAY, "Double Doodle! Google honors teachers, inventor of the eye chart," 9 May 2017
Perhaps the glasses’ increasing diopters told a narrative.

— the washington post, The Mercury News, "Was Jane Austen poisoned? New evidence about her death at 41," 13 Mar. 2017

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'diopter.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Origin and Etymology of diopter

diopter (an optical instrument), from Middle French dioptre, from Latin dioptra, from Greek, from dia- + opsesthai to be going to see — more at optic

NEW! Time Traveler

First Known Use: circa 1864

in the meaning defined above

See Words from the same year