English-language Scrabble at club level in the UK. Tournaments follow a similar structure to American ones, usually at least 6 games but weekend tournaments where players play 12 to 16 games are not uncommon. The official Scrabble association the Association of British Scrabble players sanctions official tournaments with official ratings, ratings range from about 200 to about 60. The official dictionary is called SOWPODS. In contrast to American tournaments, players do not lose a move if they challenge a valid word, which in general means more words are challenged. There are only Scrabble competitions for primary and secondary school students in Hong
Square (algebra) composition algebras. The complex square function is a twofold cover of the complex plane, such that each non-zero complex number has exactly two square roots. This map is related to parabolic coordinates. Squares are ubiquitous in algebra, more generally, in almost every branch of mathematics, and also in physics where many units are defined using squares and inverse squares: see below. Least squares is the standard method used with overdetermined systems. Squaring is used in statistics and probability theory in determining the standard deviation of a set of values, or a random variable. The deviation of each value from the