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 Club and Tournament Word List, the Official Scrabble Players Dictionary) provide a list of officially permissible words. The name Scrabble is a trademark of Hasbro, Inc. in the United States and Canada and has been sold by Hasbro's Parker Brothers division since 1999; prior to 1999 it was sold as a Milton Bradley game. Outside the United States and Canada, Scrabble is a trademark of Mattel. The game is sold in 121 countries and is available in 29 languages; approximately 150 million sets have been sold worldwide and roughly one-third of American homes have a Scrabble set.