A Latin square is an n × n array of n symbols in which every symbol appears exactly once in every row and column. section 5.4
Sudoku adapts this structure into a constraint-satisfaction problem: its 9 × 9 grid must contain digits 1 through 9 exactly once in each row and column, with an additional requirement for each 3 × 3 region. section 5.4
Sudoku as an extended Latin square
A completed Sudoku grid satisfies the Latin-square conditions across rows and columns. Its nine 3 × 3 boxes impose extra constraints, making Sudoku more restrictive than an ordinary Latin square. section 5.4
