A sunglass (or more commonly, sunglasses) refers to eyewear with darkened or polarized lenses that protect your eyes from the sun's bright light and harmful UV rays, also known as "shades," "dark glasses," or "sunnies," serving both protective and fashion purposes. In a rarer, older sense, "sunglass" can also mean a magnifying (convex) lens used to focus sunlight, like a burning glass, to create heat or start a fire.