If a player has made a play and has not yet drawn a tile, the opponent may choose to challenge any or all words formed by the play. The player challenged must then look up the words in question using a specified word source (such as OTCWL, the "Official Scrabble Players Dictionary", or CSW) and if any one of them is found to be unacceptable, the play is removed from the board, the player returns the newly played tiles to their rack, and the turn is forfeited. In tournament play, a challenge may be to the entire play or any one or more words formed in the play, and judges (human or computer) are used, so players are not entitled to know which word(s) are invalid. Penalties for unsuccessfully challenging an acceptable play vary in club and tournament play and are described in greater detail below.