A crossword is a word puzzle that usually takes the form of a square or a rectangular grid of white- and black-shaded squares. The game's goal is to fill the white squares with letters, forming words or phrases, by solving clues which lead to the answers. In languages that are written left-to-right, the answer words and phrases are placed in the grid from left to right and from top to bottom. The shaded squares are used to separate the words or phrases.

The phrase "cross word puzzle" was first written in 1862 in the United States. Crossword-like puzzles, for example Double Diamond Puzzles, appeared in the magazine St. Nicholas, published since 1873.  Another crossword puzzle appeared on September 14, 1890, in the Italian magazine Il Secolo Illustrato della Domenica. It was designed by Giuseppe Airoldi and titled "Per passare il tempo" ("To pass the time"). Airoldi's puzzle was a four-by-four grid with no shaded squares; it included horizontal and vertical clues.

On December 21, 1913, Arthur Wynne, a journalist from Liverpool, England, published a "word-cross" puzzle in the New York World that embodied most of the features of the genre as we know it. This puzzle is frequently cited as the first crossword puzzle, and Wynne as the inventor. Later, the name of the puzzle was changed to "crossword".

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