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-free word Square-free word In combinatorics, a square-free word is a word (a sequence of characters) that does not contain any subword twice in a row. Thus a square-free word is one that avoids the pattern "XX". Over a two-letter alphabet {"a, b"} the only square-free words are the empty word and "a", "b", "ab", "ba", "aba", and "bab". However, there exist infinite square-free words in any alphabet with three or more symbols, as proved by Axel Thue. One example of an infinite square-free word over an alphabet of size 3 is the word over the alphabet {0,±1} obtained by taking the