Scrabble is a word game in which two to four players score points by placing tiles, each bearing a single letter, onto a gameboard which is divided into a 15×15 grid of squares. The tiles must form words which, in crossword fashion, flow left to right in rows or downwards in columns. The words must be defined in a standard dictionary. Specified reference works (e.g., the Official Club and Tournament Word List, the Official Scrabble Players Dictionary) provide a list of officially permissible words.

The game is played by two to four players on a square board with a 15×15 grid of cells (individually known as "squares"), each of which accommodates a single letter tile. In official club and tournament games, play is between two players or, occasionally, between two teams each of which collaborates on a single rack.

Acceptable words are the primary entries in some chosen dictionary, and all of their inflected forms. Words that are hyphenated, capitalized (such as proper nouns), or apostrophized are not allowed, unless they also appear as acceptable entries; JACK is a proper noun, but the word JACK is acceptable because it has other usages as a common noun (automotive, vexillological, etc.) and verb that are acceptable. Acronyms or abbreviations, other than those that have acceptable entries (such as AWOL, RADAR, LASER, and SCUBA) are not allowed. Variant spellings, slang or offensive terms, archaic or obsolete terms, and specialized jargon words are allowed if they meet all other criteria for acceptability; though archaic spellings (e.g. NEEDE for NEED) are generally not allowed. Foreign words are not allowed in the English language Scrabble unless they have been incorporated into the English language – for example, the words PATISSERIE, KILIM, and QI. Vulgar and offensive words are generally excluded from the OSPD4, but are allowed in club and tournament play.