"prism:  "(1) a solid figure whose bases or ends have the same size and shape and are parallel to one another, and each of whose sides is a parallelogram; (2) a transparent body of this form, often of glass and usually with triangular ends, used for separating white light passed through it into a spectrum or for reflecting beams of light; (3) a cut-glass object, such as a pendant of a chandelier; (4) a crystal form consisting of three or more similar faces parallel to a single axis; (5) a medium that misrepresents whatever is seen through it.  [...from Greek prīmsa, “thing sawed off,” ...from prīzein, “to saw”]." —from The American Heritage Dictionary of the English Language, 4th Ed., 2000, p. 1396