Scrabble pt 5

Challenges
The penalty for a successfully challenged play is nearly universal: the offending player removes the tiles played and forfeits the turn. (However, in some online games, an option known as "void" may be used, wherein unacceptable words are automatically rejected by the program. The player is then required to make another play, with no penalty applied.)

The penalty for an unsuccessful challenge (where all words formed by the play are deemed valid) varies considerably, including:

The "double challenge" rule, in which an unsuccessfully challenging player must forfeit the next turn. This penalty governs North American (NASPA-sanctioned) tournaments, and is the standard for North American, Israeli and Thai clubs. Because loss of a turn generally constitutes the greatest risk for an unsuccessful challenge, it provides the greatest incentive for a player to "bluff", or play a "phony" – a plausible word that they know or suspect to be unacceptable, hoping their opponent will not call them on it. Players have divergent opinions on this aspect of the double-challenge game and the ethics involved, but officially it is considered a valid part of the game.
A pure "single challenge" or "free challenge" rule, in which no penalty whatsoever is applied to a player who unsuccessfully challenges. This is the default rule in the United Kingdom and the Republic of Ireland, as well as for many tournaments in Australia, although these countries do sanction occasional tournaments using other challenge rules.
A modified "single challenge" rule, in which an unsuccessful challenge does not result in the loss of the challenging player's turn, but is penalized by the loss of a specified number of points. The most common penalty is five points. The rule has been adopted in Singapore (since 2000), Malaysia (since 2002), South Africa (since 2003), New Zealand (since 2004), and Kenya, as well as in contemporary World Scrabble Championships (since 2001). Some countries and tournaments (including Sweden) use a 10-point penalty instead. In most game situations, this penalty is much lower than that of the "double challenge" rule; consequently, such tournaments encourage a greater willingness to challenge and a lower willingness to play dubious words.

Historic evolution of the rules
The North American "box rules" (that are included in each game box, as contrasted with tournament rules) have been edited four times: in 1953, 1976, 1989, and 1999.

The major changes in 1953 were as follows:
It was made clear that words could be played through single letters already on the board.
It was made clear that a player could play a word parallel and immediately adjacent to an existing word provided all crosswords formed were valid.
It was made clear that the effect of two word premium squares were to be compounded multiplicatively.
The previously unspecified penalty for having one's play successfully challenged was stated: withdrawal of tiles and loss of turn.
The major changes in 1976 were as follows:

It was made clear that the blank tile beats an A when drawing to see who goes first.
A player could now pass his/her turn, doing nothing.
A loss-of-turn penalty was added for challenging an acceptable play.
If final scores are tied, the player whose score was highest before adjusting for unplayed tiles is the winner.
The editorial changes made in 1989 did not affect game play.

The major changes in 1999 were as follows:
It was made clear that a tile can be shifted or replaced until the play has been scored.
It was made clear that a challenge applies to all the words made in the given play.
Playing all seven tiles is officially called a "Bingo".
In what was certainly an editorial blunder, it was made clear that a player can form more than one word in one row on a turn.