Prism

Part of speech: noun

Pronunciation: /ˈpɹɪz(ə)m/

Definitions

1. A solid geometric figure with two parallel and congruent polygonal bases connected by rectangular faces ; a transparent optical device that bends light and splits it into its spectral colors
2. A three-dimensional shape featuring two parallel polygonal ends linked by parallelogram sides ; a piece of glass or other transparent material used to refract light and separate it into a rainbow of colors
3. A polyhedral form having matching polygonal faces at the top and bottom joined by rectangular sides ; an item used in optics to change the direction of light and break it into its constituent hues

Etymology: The Greek word "prisma" literally meant "anything sawn," including sawdust, so the glass object is named after the act of cutting. It came from "prizein" or "prio," a verb meaning "to saw," and the suffix "-ma," which forms nouns for the result of an action. A prism is, in effect, a sawn-off piece of a solid shape. The word passed into Late Latin as "prisma," where it took on the geometric sense of a solid with parallel sides. English borrowed it directly from that Latin form as a learned term, and it kept its geometric meaning before the optical sense of a transparent wedge that splits light into colors became dominant. The connection between the two is simple: a glass prism is a solid whose faces are cut at angles, the very kind of shape the Latin term named.

Synonyms: figured glass, optical element