optic

1. (archaic, humorous) An eye.Examples: "The difference is as great between / The optics seeing, as the object seen."; "how they, / Who saw those figures on the margin kiss all, / Could turn their optics to the text and pray, / Is more than I know[…]"; "Elbows almost touching they leaned at ease, idly reading the almost obliterated lines engraved there. ¶ "I never understood it," she observed, lightly scornful. "What occult meaning has a sun-dial for the spooney? I'm sure I don't want to read riddles in a strange gentleman's optics.""

2. (optics) A lens or other part of an optical instrument that interacts with light.Examples: "The single-imaging optic of the mammalian eye offers some distinct visual advantages. Such lenses can take in photons from a wide range of angles, increasing light sensitivity. They also have high spatial resolution, resolving incoming images in minute detail."

3. (trademark in UK) A measuring device with a small window, attached to an upside-down bottle, used to dispense alcoholic drinks in a bar.Examples: "They were neatly lined up on three shelves between the optics of martini, vodka, whisky and gin."; "They pulled up two bar stools and looked around the room as the barman relieved the whisky optic of its contents."