Twenty questions is a spoken parlor game, which encourages deductive reasoning and creativity. It originated in the United States and was played widely in the 19th century. It escalated in popularity during the late 1940s, when it became the format for a successful weekly radio quiz program.

In the traditional game, the "answerer" chooses something that the other players, the "questioners", must guess. They take turns asking a question which the answerer must answer with "yes" or "no". In variants of the game, answers such as "maybe" are allowed. Sample questions could be: "Is it bigger than a breadbox?", "Is it alive?", and finally "Is it this pen?" Lying is not allowed. If a questioner guesses the correct answer, they win and become the answerer for the next round. If 20 questions are asked without a correct guess, then the answerer has stumped the questioners and gets to be the answerer for another round.

Careful selection of questions can greatly improve the odds of the questioner winning the game. For example, a question such as "Does it involve technology for communications, entertainment or work?" can allow the questioner to cover a broad range of areas using a single question that can be answered with a simple "yes" or "no", significantly narrowing down the possibilities.