Name that Polyhedron!

For recent design project I spent the better part of a day trying to find out the name of a 72 faced shape. Finding the schema for naming a 2 dimensional shape, also known as a polygon, by its number of faces was easy; wikipedia had a brief naming table. Finding a similar table for a 3 dimensional shape, or polyhedron, was a lot harder (I actually had to use a book!) but very obvious when I found it.

Polyhedron & Polygon Naming Conventions

Having a table of naming information is useful but learning the rules behind how they are named makes things much easier to remember so I’ve summed up my observations.

  1. Both regular poly shapes are named from largest number to smallest, that is hundreds, tens, units
  2. Polygons can use the ‘kai’ conjunctive between Tens and Units .e.g. tetracontakaidigon and tetracontadigon are both valid for a 42 faced shape
  3. Polyhedrons end in ‘hedron’.
  4. Polygons end in ‘gon’.

For numbers greater than the table I’ve provided and the one available on wikipedia you multiply each digit by its base and call it as such so 4,000 faces becomes 4 × 1000 and called tetra × chilia + gon, 300 faces becomes 3 × 100 called tri × hecto + gon.

Table you can use from left to right for naming shaped 1-100
Tens and Units final suffix
10 deca- 1 -hena- -gon
20 icosi- -kai- 2 -di-
30 triaconta- 3 -tri-
40 tetraconta- 4 -tetra-
50 pentaconta- 5 -penta-
60 hexaconta- 6 -hexa-
70 heptaconta- 7 -hepta-
80 octaconta- 8 -octa-
90 enneaconta- 9 -ennea-
100 hecto- 0

For numbers great than one hundred you can use this base numbers.

Name Value
100 hecto
1,000 chilia
10,000 myria

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