SINCE 1828
dictionary
thesaurus

diopter

noun
Save Word
di·​op·​ter | \ dī-ˈäp-tər How to pronounce diopter (audio) , 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

Examples of diopter in a Sentence

Recent Examples on 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, 9 May 2017 Perhaps the glasses’ increasing diopters told a narrative. — The Washington Post, The Mercury News, 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.

First Known Use of diopter

circa 1864, in the meaning defined above

History and Etymology for 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

Buying Guide

Our Reviews team has selected the best digital cameras.

Learn More About diopter

Time Traveler for diopter

Time Traveler

The first known use of diopter was circa 1864

See more words from the same year

Dictionary Entries Near diopter

dioptase

diopter

dioptral

See More Nearby Entries 

Statistics for diopter

Cite this Entry

“Diopter.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/diopter. Accessed 30 Jun. 2022.

Style: MLA
MLACheck Mark Icon ChicagoCheck Mark Icon APACheck Mark Icon Merriam-WebsterCheck Mark Icon

More Definitions for diopter

diopter

noun
di·​op·​ter
variants: or chiefly British dioptre \ dī-​ˈäp-​tər, ˈdī-​ˌäp-​ How to pronounce diopter (audio) \

Medical Definition of diopter

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

More from Merriam-Webster on diopter

Britannica.com: Encyclopedia article about diopter

WORD OF THE DAY

scintillate

Listen to the pronunciation of scintillate

See Definitions and Examples »

Test Your Vocabulary

Which Word Does Not Belong?

  • one green toy robot amidst many red toy robots
  • Which of these words does not mean "nonsense"?
Name That Thing

Test your visual vocabulary with our 10-question challenge!

TAKE THE QUIZ
Universal Daily Crossword

A daily challenge for crossword fanatics.

TAKE THE QUIZ
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

Words at Play
Ask the Editors
Word Games