The term 'diamond square' is a type of tessellation pattern that is used in quilting and other forms of textile art. It is created by taking a square and dividing it into four equal parts, then adding a diamond shape in the center. The result is a pattern of diamonds and squares that can be repeated to create a larger design. The BASE of this pattern is a four-letter word, which is often referred to as the 'BASE square.' This BASE square is the foundation for the entire pattern and is used to create the diamond shapes.