A square number is a number that can be expressed as the product of an integer multiplied by itself. For example, the number 4 is a square number because it can be written as 2 × 2. Other examples include 1 (1 × 1), 9 (3 × 3), and 16 (4 × 4). Square numbers are important in mathematics and appear in various areas, such as geometry and algebra. They can be represented visually as squares on a grid, where the length of each side corresponds to the integer. The sequence of square numbers starts with 0, 1, 4, 9, and continues indefinitely.