A crossword is a word puzzle and word search game 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.

A traditional crossword is made up of black and white squares, called a grid. All the white squares appear in horizontal rows or vertical columns, but are not always separated with black squares. Another way to say this is that every white square must have at least one other white square touching it on any side. The kind of crossword that appears in newspapers and magazines, such as the one in the image, often has lots of white squares beside each other.

The goal of solving the puzzle is to write different words, letter-by-letter, in the white squares. Next to the grid is a list of clues. The answer to each clue is a word or sometimes a phrase.

There are many types of crosswords. Straight (or Quick) crosswords are usually made up of simple definitions - which means that other words are used to describe the answer. Some crosswords, called cryptic crosswords, use riddles and word play and are usually more difficult than straight crosswords.