Scrabble is a word game in which two to four players score points by placing tiles, each bearing a single letter, onto a gameboard which is divided into a 15×15 grid of squares. The tiles must form words which, in crossword fashion, flow left to right in rows or downwards in columns. The words must be defined in a standard dictionary. Specified reference works (e.g., the Official Tournament and Club Word List, the Official Scrabble Players Dictionary) provide a list of officially permissible words.