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 variants or triplets of numbers that sum up to less than, or exactly 15, respectively. The placement of the pairs or triplets is similar to Scrabble. Triolet means "triplet" in French. Yushino uses number sequences where every number is the last digit of the sum of the previous two. For two number sequences it requires that the numbers are adjacent. Mixmath, a game developed by Wrebbit, also involves placing correct mathematical equations on a board with bonus squares similar to a scrabble board. Scrabble Upwords (originally just named UpWords) is played with 100 letter tiles on a special 10×10 board with