A crossword is a puzzle in which words are guessed from given definitions or clues. Words are then fitted into a sequence of black and white squares that results in creation of interlocked vertical and horizontal patterns. Crossword puzzles include definitions of words written horizontally as well as words written vertically. Crossword grids appearing in most North American publications have a significantly lesser number of black squares than those published in Australia or Britain.

The major variants of crosswords are cipher crosswords, diagram-less crosswords, fill-in crosswords, and cross numbers. Cross numbers is the numerical counterpart of crosswords. Crosswords can also be differentiated on the basis of the type of clues. Crossword clues can either be straight or quick, comprising of clear definition of the answer, or they can be cryptic or indirect comprising of metaphorical meaning or pure wordplay.

The early version of crosswords that was devised in Britain in nineteenth century was based on an ancient word square. The form of crosswords prevalent nowadays was developed in United States by Arthur Wynne in 1913. This puzzle was published in New York World, and it included most of the features present in crosswords of today. Subsequently, crossword puzzles became a very popular feature of the publication.

The first book of crosswords puzzles was compiled and published in 1924, by Simon and Schuster. Publication of this book further helped crosswords in becoming a worldwide craze. The New York Times crossword puzzle has been running since 1942, and is considered the most prestigious and most difficult to solve among crossword puzzles. The popularity of crosswords has given birth to many popular games such as scrabble.