bifocal

[bahy-foh-kuhl, bahy-foh-]
adjective
1.
Chiefly Optics. having two foci.
2.
(of an eyeglass or contact lens) having two portions, one for near and one for far vision.
noun
3.
bifocals, bifocal eyeglasses or contact lenses.

Origin:
1885–90, Americanism; bi-1 + focal

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World English Dictionary
bifocal (baɪˈfəʊkəl)
 
adj
1.  optics having two different focuses
2.  relating to a compound lens permitting near and distant vision

Collins English Dictionary - Complete & Unabridged 10th Edition
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Etymonline
Word Origin & History

bifocal
1888, from bi- + focal (see focus).
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Medical Dictionary

bifocal bi·fo·cal (bī-fō'kəl, bī'fō'-)
adj.

  1. Having two focal lengths.

  2. Having one section that corrects for distant vision and another that corrects for near vision.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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Example sentences
Without bifocal vision, he lacked depth perception and couldn't tell how far ahead of him horses were.
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