Scrabble is a word game in which two to four players score points by forming words from individual lettered tiles on a game board marked with a 15-by-15 grid. The words are formed across and down in crossword fashion and must appear in a standard dictionary. Official reference works (e.g. The Official Scrabble Players Dictionary) provide a list of permissible words.
The board with a 15-by-15 grid of cells (individually known as "squares"), each of which accommodates a single letter tile.
The board is marked with "premium" squares, which multiply the number of points awarded: dark red "triple-word" squares, pink "double-word" squares, dark blue "triple-letter" squares, and light blue "double-letter" squares. The center square is often marked with a star or logo, and counts as a double-word square.
The game contains 100 tiles, 98 of which are marked with a letter and a point value ranging from 1 to 10. The number of points of each lettered tile is based on the letter's frequency in standard English writing.
Commonly used letters such as E or O are worth one point, while less common letters score higher, with Q and Z each worth 10 points. The game also has two blank tiles that are unmarked and carry no point value. The blank tiles can be used as substitutes for any letter; once laid on the board, however, the choice is fixed.
Next, players decide the order in which they play. Each player to draws a tile: the player who picks the letter closest to the beginning of the alphabet goes first (with blank tiles ranked higher than A's).
At the beginning of the game, and after each turn until the bag is empty (or until there are no more face-down tiles), players draw tiles to replenish their "racks, with seven tiles, from which they will make plays. Each rack is concealed from the other players.
During a turn, a player will have seven or fewer letter tiles in their rack from which to choose a play. On each turn, a player has the option to: (1) pass, forfeiting the turn and scoring nothing; (2) exchange one or more tiles for an equal number from the bag, scoring nothing, an option which is only available if at least seven tiles remain in the bag; or (3) form a play on the board, adding its value to the player's cumulative score.
A proper play uses any number of the player's tiles to form a single continuous word ("main word") on the board, reading either left-to-right or top-to-bottom. The main word must either use the letters of one or more previously played words, or else have at least one of its tiles horizontally or vertically adjacent to an already played word. If words other than the main word are newly formed by the play, they are scored as well, and are subject to the same criteria for acceptability.
When the board is blank, the first word played must cover the center square. The word must consist of at least two letters, extending horizontally or vertically. The centre square is a premium square, so the first player to play a word receives a double score.
A blank tile may take the place of any letter. It remains as that letter thereafter for the rest of the game. Individually, it scores no points regardless of what letter it is designated, and is not itself affected by premium tiles. However, its placement on a double-word or triple-word square does cause the appropriate premium to be scored for the word in which it is used.
After playing a word, the player draws letter tiles from the bag to replenish his rack to seven tiles. If there are not enough tiles in the bag to do so, the player takes all of the remaining tiles.
After a player plays a word, his opponent may choose to challenge any or all the words formed by the play. If any of the words challenged is found to be unacceptable, the play is removed from the board, the player returns the newly played tiles to his rack and his turn is forfeited.
When the game ends, each player's score is reduced by the sum of his/her unplayed letters. In addition, if a player has used all of his or her letters, the sum of the other player's unplayed letters is added to that player's score; in tournament play, a player who "goes out" adds double this sum, and the opponent is not penalized.
Scoreless turns can occur when an illegal word is challenged off the board, when a player passes or when a player exchanges tiles or in the unlikely event that only a blank or blanks are played.
