A Latin square is a grid arrangement used in statistics and experimental design, where each symbol appears exactly once in each row and column. Typically, the symbols are numbers or letters, and the size of the square is defined by the number of symbols used. For example, a 3x3 Latin square might use the symbols 1, 2, 3. Latin squares are useful for controlling variables in experiments, helping to reduce bias and improve the reliability of results. They are commonly applied in fields like agriculture, psychology, and education to ensure that each treatment or condition is tested under various circumstances.