TESSELLATION
Another word for tiling. Importantly, the shapes in a tessellation don’t overlap. There are also no gaps. The most common shape used in a tessellation is therefore a square, equilateral triangle or a hexagon. What these shapes have in common: Their sides are equal. Their interior angles are equal. These are called ‘regular’ tessellations.
But then you’ve got your ‘semi regular’ tessellations. There are only eight of them. (You can look em up.)
It gets more complicated when you get into your demi-regular tessellations and your polymorph tessellations. Think M.C. Escher.