An arrangement in a plane of

*n*equilateral triangles joined to one another by at least one of their sides.The order of a polyiamond corresponds to the number of triangles assembled in a configuration.

Polyiamond of order 3 or *triamond*

Naming polyiamonds

- Order of 1 (one triangle): moniamond
- Order of 2 (2 triangles): diamond
- Order of 3 (3 triangles): triamond
- Order of 4 (4 triangles): tetriamond
- Order of 5 (5 triangles): pentiamond
- Order of 6 (6 triangles): hexiamond
- Etc.