# hexa-

The Greek suffix hexa- means 'six'. A **hexagon** is a six-sided polygon. A **hexahedron** is
a six-sided polyhedron, otherwise known
as a cube if it is regular. **Hexadecimal** is the number system with base 16
(i.e., six more than decimal system) and is used mostly in computing (because
four binary digits can represent 16 different numbers). **Hexagonal
numbers** are figurate numbers (numbers that can be represented by a regular geometric arrangement of equally
spaced points) of the form *n*(2*n* – 1); the first few are
1, 6, 15, 28, 45, ... For **hexaflexagon** see flexagon.
For **hexomino** see polyomino.