op·ti·cal·ly \ˈäptə̇k(ə)lē, -tēk-, -li\adverb Etymology:optical + -ly 1.: by means of sight : with or to the eye < as viewed optically > < an optically accurate measurement > 2.: with reference to or by means of optics or to optical properties < vitamins measured optically > < optically ground surfaces > — compare optically active