Number & MeasureGreek → English
Octahedron
/ˌɑːktəˈhiːdrən/noun
A solid with eight triangular faces, like two square pyramids glued base to base.
The Greek roots
ὀκτώ
oktṓ
eight
ἕδρα
hédra
seat, base
Literally: “eight seats”
The story of the word
The faces are called seats because a solid sits on them. ἕδρα is an ordinary word for a chair or a sitting, and it turns up in church architecture too: a cathedral is the building that holds the bishop's seat. Plato assigned the octahedron to air in the Timaeus, on the grounds that air is finer than earth and coarser than fire. English has the word from the 1570s.
- How it travelled
- Ancient Greek → Latin → English
- First recorded
- 1570s
The same roots elsewhere
Other languages reached for exactly the same Greek pieces.
Same family
cathedralpolyhedrontetrahedronoctopus
In a sentence
Fluorite grows naturally as an octahedron, which makes it look manufactured.
He folded the paper into a lopsided octahedron and called it done.