I. adjective Date: 1826 having three focal lengths II. noun Date: 1899 1. plural eyeglasses with trifocal lenses 2. a trifocal glass or lens

New Collegiate Dictionary. 2001.

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  • trifocal — ☆ trifocal [trī fō′kəl; ] also, and for n. usually [, trī′fō΄kəl ] adj. adjusted to three different focal lengths n. a lens like a bifocal but with an additional narrow area ground to adjust the intermediate focus for objects at c. 76 cm ( c. 30… …   English World dictionary

  • trifocal — Having three foci. See t. lens. * * * tri·fo·cal ( )trī fō kəl adj 1) having three focal lengths 2) of an eyeglass lens having one part that corrects for near vision, one for intermediate vision (as at arm s length), and one for distant vision… …   Medical dictionary

  • Trifocal — Trifocals are eyeglasses where the lenses have 3 regions to correct for distance, intermediate (arm s length), and near vision. They are mostly used by people with advanced presbyopia who have been prescribed 2 diopters or more of reading… …   Wikipedia

  • trifocal — /truy foh keuhl, truy foh /, adj. 1. Optics. having three foci. 2. (of an eyeglass lens) having three portions, one for near, one for intermediate, and one for far vision. n. 3. trifocals, eyeglasses with trifocal lenses. [1945 50; TRI + FOCAL] * …   Universalium

  • trifocal — adjective (of a pair of glasses) having lenses with three parts with different focal lengths. noun (trifocals) a pair of trifocal glasses …   English new terms dictionary

  • trifocal — tri•fo•cal [[t]traɪˈfoʊ kəl, ˈtraɪˌfoʊ [/t]] adj. 1) opt (of a lens) having three foci 2) (of an eyeglass lens) having three portions, one for near, one for intermediate, and one for far vision 3) trifocals, eyeglasses with trifocal lenses •… …   From formal English to slang

  • trifocal — adj. & n. adj. having three focuses, esp. of a lens with different focal lengths. n. (in pl.) trifocal spectacles …   Useful english dictionary

  • trifocal — adjective Of or pertaining to corrective lenses that have three different powers per eye. See Also: bifocal, trifocals …   Wiktionary

  • trifocal — adj. concerning an eyeglass lens with three portions (for seeing far, intermediate and near); having three focal lengths …   English contemporary dictionary

  • trifocal — tri·focal …   English syllables

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