The name Scrabble is a trademark of Hasbro, Inc. in the US and Canada and of J. W. Spear & Sons PLC elsewhere for a board game in which players use 100 tiles with printed letters to form words on a 15 x 15 grid with certain "premium" squares to accumulate points.
The game was invented by architect Alfred Mosher Butts in 1938, as a variation on an earlier word game he invented called "Lexico". Both games shared the set of letter tiles, whose distributions and point values Butts worked out meticulously by counting letter usage from the New York Times and other sources. The new game, which he called "Criss-Crosswords", added the 15-by-15 game board and the crossword-style game play. He manufactured a few sets himself, but was not successful in selling the game to any major game manufacturers of the day.
In 1948, lawyer James Brunot bought the rights to manufacture the game in exchange for granting Butts a royalty on every unit sold. Though he left most of the game (including the distribution of letters) unchanged, Brunot slightly rearranged the "premium" squares of the board and simplified the rules; he also changed the name of the game to "Scrabble", and sold sets to, among other customers, Macy's department store, which created a demand for the game.
In 1953, unable to meet demand himself, Brunot sold manufacturing rights to Selchow and Righter (one of the manufacturers who, like Parker Brothers and Milton Bradley, had previously rejected the game). J. W. Spear & Sons began selling the game in Australia and the UK in 1953. They are now a subsidiary of Mattel, Inc.
In 1986, Selchow and Righter sold the game to Coleco, who soon after sold the game to Hasbro.
The game is played on a square (or nearly square) board with a 15 x 15 grid of cells, each of which is just large enough to accommodate a single letter tile. In the notation system common in tournament play, the vertical columns of the board are labelled A through O, and the horizontal rows from 1 to 15. Certain cells of the board are "premium" cells that affect scoring. Specifically, cells A1, H1, O1, A8, O8, A15, H15, and O15 are "triple word" squares, typically colored dark red; B2, N2, C3, M3, D4, L4, E5, K5, H8, E11, K11, D12, L12, C13, M13, B14, and N14 are "double word" cells, colored pink; F2, J2, B6, F6, J6, N6, B10, F10, J10, N10, F14, and J14 are "triple letter" cells, colored dark blue; and D1, L1, G3, I3, A4, H4, O4, C7, G7, I7, M7, D8, L8, C9, G9, I9, M9, A12, H12, O12, G13, I13, D15, and L15 are "double letter" cells, colored light blue. The center cell H8 is often marked with a star or logo.
English language editions of the game contain 100 letter tiles, in the following distribution: 2 "blank" tiles (scoring 0 points), 9 As (1 point), 2 Bs (3), 2 Cs (3), 4 Ds (2), 12 Es (1), 2 Fs (4), 3 Gs (2), 2 Hs (4), 9 Is (1), 1 J (8), 1 K (5), 4 Ls (1), 2 Ms (3), 6 Ns (1), 8 Os (1), 2 Ps (3), 1 Q (10), 6 Rs (1), 4 Ss (1), 6 Ts (1), 4 Us (1), 2 Vs (4), 2 Ws (4), 1 X (8), 2 Ys (4), and 1 Z (10). Editions in other languages vary greatly. During play, the letter tiles are kept in an opaque cloth bag from which the players draw to fill their "racks" of seven tiles from which they will make plays.
At the beginning of each player's turn in the game, each player will have seven letter tiles in his rack from which to choose a play. The tiles in each player's rack are concealed from the other players. At each player's turn, he has the option to (1) pass, forfeiting his turn and scoring nothing; (2) exchange one or more of the tiles in his rack for an equal number from the bag, providing there are at least seven tiles remaining in the bag, scoring nothing; or (3) play a word, adding its value to his score. To play a word, the player must use from one to seven of his tiles to form a single continuous word on the board, either left-to-right or top-to-bottom (possibly using tiles already played). The word played must touch one or more already-played words on the board, and any other words formed by the play must be legal words and are scored as well (need pictures and examples here). (The first player, who has no previously played words to touch, must form a legal word of two to seven letters from the tiles in his rack, and place it on the board in contiguous cells either left-to-right or top-to-bottom, and including center cell H8).
Each word formed in the play is scored this way: first, any tile played from the player's rack onto a previously vacant cell that is a "double letter" or "triple letter" premium cell has its point value doubled or tripled as indicated. To this is added the normal point value of every other letter in the word (whether newly played or existing). Then, if any newly-played tile was placed on a "double word" premium cell, the total is doubled. Likewise if any newly-placed tile was on a "triple word" premium cell, the total is tripled. If two newly-placed tiles in the word are played on double-word cells, the total is doubled, and then redoubled, scoring four times the letter total. Likewise, a word played with two new tiles on triple-word cells is tripled and then retripled for nine times the letter score. In the unlikely but possible event that a 15-letter word is formed using new tiles on three triple-word cells (this requires using at least eight previously placed letters on other cells), the letter score is multiplied by twenty-seven. It is not possible for double word and triple word cells to be used in the same word (since there are no such cells in the same row or column of the board). Finally, if a player uses all seven of the tiles in his rack in a single play, a bonus of 50 points is added to the score of that play (this is called a "bingo").
A blank tile may be designated by the player as any letter; it retains that value thereafter for the rest of the game. As a letter, it scores no points (even doubled or tripled) regardless of what letter it is designated, but its placement on a double-word or triple-word cell does cause the appropriate premium to be scored for the word in which it is used. While not part of official or tournament play, a common "house rule" allows players to "recycle" blank tiles by later substituting the tile for the letter it designates.
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 formed are 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. If all words are acceptable, then the challenger forfeit his turn (this rule varies in international play).
The game ends whenever (1) one player plays every tile in his rack, and there are no tiles remaining in the bag (regardless of the tiles in his opponent's rack); or (2) when six turns have passed without either player being able to play a word. In the first case, the player who "goes out" receives a bonus of twice the point value of his opponent's remaining tiles. (This rule also varies slightly in international play).
Acceptable words are those words found as primary entries in some chosen dictionary, and all of their inflected forms. Words that are hyphenated, capitalized (such as proper nouns), marked as foreign, or appear only as part of multi-word phrases are not allowed (unless they also appear as acceptable entries: "Japan" is a proper noun, but the verb "japan"--to decorate with black enamel or lacquer--is acceptable). Variant spellings, slang or offensive terms, archaic terms, and specialized jargon words are allowed if they meet all other criteria for acceptability. "College" level dictionaries are generally used in preference to unabridged dictionaries.
In formal competition, pre-compiled official word lists are used (usually compiled from combinations of several college dictionaries), along with an official dictionary for backup. The pre-compiled word lists generally contain only words of two to eight letters--those most frequently used in the game. The dictionary is consulted for longer words. There are two popular competition word lists: the American 1998 word list (on which the Official Scrabble Players Dictionary, Third Edition (OSPD3) is based, and the British Official Scrabble Words. American competitions usually use Funk & Wagnall's College Dictionary for longer words, while the British use Chambers. The OSPD3 available in bookstores differs from the official competition word list in that it is marketed for "home and school" use, and has been expurgated of many words judged offensive. These are still legal in competition. Many international competitions use both the British and American word lists.
There are two primary forms of tournament Scrabble. American tournaments have one set of rules and legal word list, and international games have a separate set of rules and legal words. The international word list is a superset of the American word list. The primary rules variation is that in international play, a player may "challenge" an opponent's play if he suspects it is not a legal word without risking a penalty if the word is acceptable. In American play, a failed challenge results in a loss of turn, making it possible to "bluff" with a illegal word in the hope your opponent will be afraid to challenge.