Convention (bridge)

Calls made during the auction phase of a contract bridge game convey information about the player's card holdings. Calls may be "natural" (that is, are based on a holding of the suit bid, or a balanced distribution in the case of a notrump bid) or "artificial" (show a feature unrelated to the named denomination). A bridge convention is an agreement about an artificial call or a set of related artificial calls.

Contract bridge is a trick-taking card game played by four players in two competing partnerships in which a sequence of bidding, also known as the auction, precedes the play of the cards. The purpose of this bidding is for players to inform their partners of the content of their hand and to arrive at a suitable contract at which to play the hand (or to prevent the opponents from arriving at a suitable contract). Although bidding is often "natural" (describing a hand by simple reference to possession, shape, and strength of the named suit) players may also bid using conventions, which assign more specific information to certain calls, particularly at the more advanced levels of competitive play. Bill Root defines "convention" as, "A specific agreement between partners to give an unusual meaning to a bid". However, some conventions, for example, Stayman, are very widely used and cannot be said to be unusual.

Conventions are often named after their ostensive author (the Drury convention), their promulgator (the Stayman convention), or something about the methodology itself (the strong two clubs convention).

The term conventional is also used to describe certain opening leads, discards and signals that have specific agreed meanings.

Conventions to be played must be agreed by partners before play begins and must be disclosed to their opponents, either in advance by the use of convention cards or by alerts, announcements, and answers to questions about one's partner's bids once bidding has begun. Generally, this disclosure also must include the negative implications of choosing the bid over another alternative. Failure to reveal fully the existence and meaning of a convention generally constitutes an illegal communication of information between partners.

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