Text: 1. A solid whose bases or ends are similar plane figures and whose sides are parallelograms. 2. In optics, a transparent solid with tirangular ends and two converging sides. It breaks up (or differentiates) white (undifferentiated) light into its component colors, and bends the rays of light toward the side opposite the angle (the base of the prism), and is used to measure or correct imbalance of the ocular muscles, as in glasses.

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