Scrabble have been sold worldwide and roughly one-third of American and half of British homes have a Scrabble set. There are around 4,000 Scrabble clubs around the world. The game is played by two to four players on a square board with a 15×15 grid of cells (individually known as "squares"), each of which accommodates a single letter tile. In official club and tournament games, play is between two players or, occasionally, between two teams each of which collaborates on a single rack. The board is marked with "premium" squares, which multiply the number of points awarded: eight dark red "triple-word"
Scrabble generally excluded from the OSPD4 but allowed in club and tournament play. Proper nouns and other exceptions to the usual rules are allowed in some limited contexts in the spin-off game "Scrabble Trickster". Names of recognized computer programs are permitted as an acceptable proper noun (For example, WinZIP). There are two popular competition word lists used in various parts of the world: TWL and SOWPODS (also called "Collins" or "CSW"). The memorization of two-letter words is considered an essential skill in this game. The North American 2006 "Official Tournament and Club Word List, Second Edition" (OWL2) went into official use