Having three foci. See t. lens.

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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
trifocal n
1) a trifocal glass or lens
2) trifocals pl eyeglasses with trifocal lenses

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tri·fo·cal (tri-foґ-) (triґfo-kəl) 1. having three foci. 2. containing one part for near vision, one for intermediate, and a third for distant vision; see under lens.

Medical dictionary. 2011.

Look at other dictionaries:

  • 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 — 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

  • 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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