Other forms: prisms
A prism is a block of clear glass with flat, angled sides. Shine a beam of white light in at one face and it comes out of another spread into a band of colours, which is the picture on the cover of Dark Side of the Moon and the reason school physics labs own so many of them.
In geometry the word is wider: a prism is any solid with two identical parallel ends joined by flat faces, so a triangular prism, a hexagonal prism and an ordinary box all count. There is a figurative use as well, in the phrase through the prism of, meaning seen and bent by one particular point of view, as in history through the prism of class. The adjective prismatic describes light split into rainbow colours. The plural is prisms.
1nounprismA transparent triangular block that splits white light into the colours it is made of.
“He held the prism up to the window and threw a rainbow across the ceiling.”
2nounsolidA solid figure with two identical parallel ends joined by flat faces.
“A triangular prism has two identical ends and three flat sides.”
3nounparticularA particular point of view that shapes how something is seen.
“She reads every family argument through the prism of her own childhood.”
Too few real examples of this word to estimate which sense is commonest.
prism is a solid geometric shape.
Prism came from Latin prisma, and before that Ancient Greek prisma, which meant anything sawn, and even sawdust, from the verb prio, to saw. The geometers borrowed the word for a solid that looks like a length sawn off a longer bar. So the thing that makes rainbows is named, plainly, after cutting wood.
Proto-Indo-European
*per-
Latin
prisma
English, today
prism
Built from
Learned borrowing from Latin prisma. Latin prisma (“(geometry) prism”), from Ancient Greek πρίσμᾰ (“anything sawn; sawdust; (Koine, geometry) prism”), from πρῐ́ζω (a variant of πρῑ́ω (“to saw”), further etymology unknown) + -μᾰ.
Etymology from Wiktionary, CC BY-SA