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.
[Late Latin prīsma, from Greek prīsma, thing sawed off, prism, from prīzein, to saw, variant of prīein.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.