Triangles

Triangles have one less side than squares. :( However, they can still tile the plane. Specifically, right triangles can because they can, if arranged properly, make a square. (So do equilateral triangles, squares, and many others)

Other types of triangles can also tile the plane. Those being:

• Equilateral triangles
• Regular triangles (They make hexagons)

Fun fact about tirangles: They make almost every single mesh you see in any 3D game. This is because a triangle always makes a plane.