Scrabble the Game, Part 3

Sequence of play
Before the game, the letter tiles are either put in an opaque bag or placed face down on a flat surface. Opaque cloth bags and customized tiles are staples of clubs and tournaments, where games are rarely played without both.

Next, players decide the order in which they play. The normal approach is for players to draw tiles: the player who picks the letter closest to the beginning of the alphabet goes first (with blank tiles ranked higher than A's). In North American tournaments, the rules of the US-based North American Scrabble Players Association (NASPA) stipulate instead that players who have gone first in the fewest number of games in the tournament have priority, or failing that, those who have gone second the most. In the case of a tie, tiles are drawn as in the standard rules.

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", or tile-holders, 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 H8, the center square. The word must consist of at least two letters, extending horizontally or vertically. H8 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. While not allowed in official or tournament play, a common "house rule" allows players to "recycle" blank tiles by later substituting the corresponding letter tile.

After playing a word, the player draws letter tiles from the bag to replenish their 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, their 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 their rack and their turn is forfeited. In tournament play, a challenge is to the entire play rather than any one word, so a judge (human or computer) is used, and players are not entitled to know which word or words caused the challenge to succeed. Penalties for unsuccessfully challenging an acceptable play vary within club and tournament play, and are described in greater detail below.

With North American rules, the game ends when (1) one player plays every tile in their rack, and there are no tiles remaining in the bag (regardless of the tiles in their opponent's rack); or (2) when six successive scoreless turns have occurred and the score is not zero-zero.

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 a player passes, when a player exchanges tiles, or when a player loses a challenge. The latter rule varies slightly in international tournaments.