tri·fo·cal 
(trī-fōkəl, trīfō′-)
(trī-fōkəl, trīfō′-)adj.
1. Having three focal lengths.
2. Having one section that corrects for distant vision, a second section that corrects for medium vision, and a third that corrects for near vision, as an eyeglass lens.
n.
1. A lens having three focal lengths.
2. trifocals Eyeglasses having trifocal lenses.
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