# Triangular tiling

Conway calls it a **deltille**, named from the triangular shape of the Greek letter delta (Δ). The triangular tiling can also be called a **kishextille** by a kis operation that adds a center point and triangles to replace the faces of a hextille.

It is one of three regular tilings of the plane. The other two are the square tiling and the hexagonal tiling.

There are 9 distinct uniform colorings of a triangular tiling. (Naming the colors by indices on the 6 triangles around a vertex: 111111, 111112, 111212, 111213, 111222, 112122, 121212, 121213, 121314) Three of them can be derived from others by repeating colors: 111212 and 111112 from 121213 by combining 1 and 3, while 111213 is reduced from 121314.^{[1]}

There is one class of Archimedean colorings, 111112, (marked with a *) which is not 1-uniform, containing alternate rows of triangles where every third is colored. The example shown is 2-uniform, but there are infinitely many such Archimedean colorings that can be created by arbitrary horizontal shifts of the rows.

The vertex arrangement of the triangular tiling is called an A_{2} lattice.^{[2]} It is the 2-dimensional case of a simplectic honeycomb.

The A^{*}_{2} lattice (also called A^{3}_{2}) can be constructed by the union of all three A_{2} lattices, and equivalent to the A_{2} lattice.

The vertices of the triangular tiling are the centers of the densest possible circle packing.^{[3]} Every circle is in contact with 6 other circles in the packing (kissing number). The packing density is π⁄√12 or 90.69%. The voronoi cell of a triangular tiling is a hexagon, and so the voronoi tessellation, the hexagonal tiling, has a direct correspondence to the circle packings.

The planar tilings are related to polyhedra. Putting fewer triangles on a vertex leaves a gap and allows it to be folded into a pyramid. These can be expanded to Platonic solids: five, four and three triangles on a vertex define an icosahedron, octahedron, and tetrahedron respectively.

It is also topologically related as a part of sequence of Catalan solids with face configuration Vn.6.6, and also continuing into the hyperbolic plane.

Like the uniform polyhedra there are eight uniform tilings that can be based from the regular hexagonal tiling (or the dual triangular tiling).

Drawing the tiles colored as red on the original faces, yellow at the original vertices, and blue along the original edges, there are 8 forms, 7 which are topologically distinct. (The *truncated triangular tiling* is topologically identical to the hexagonal tiling.)

The first is made of 2-edges, and next two are triangular edges, and the last has overlapping hexagonal edges.