Wiktionary:Word of the day/2025/March 1

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prism n

(geometry) A polyhedron with parallel ends of the same polygonal shape and size, the other faces being parallelogram-shaped sides. An object having the shape of a geometrical prism (sense 1). (construction) A cutting (“open passage at a level lower than the surrounding terrain, dug for a canal, railway, or road to go through”) or an embankment shaped like a prism (sense 1) or a number of prisms, such that its volume can be easily calculated. (crystallography) A crystal in which the faces are parallel to the vertical axis. (optics) A transparent block in the shape of a prism (sense 1), typically with triangular ends, used to reflect or refract light. (archaic) A spectrum produced by light being refracted through a prism. (by extension, surveying) A retroreflector (“device which reflects light back to its source with minimum scattering”) which is usually attached to a surveying pole as a target for a total station which emits a light beam at the device and calculates how long it takes to be reflected back in order to measure distance. (figurative) A perspective that colours one's perception. The English rock band Pink Floyd’s album The Dark Side of the Moon, which features a prism on its cover, was released on this day in 1973.

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