Bridge conventions are artificial calls in the game of bridge.
In the partnership trick-taking card game of contract bridge, a sequence of bidding precedes the play of each hand; the purpose of this bidding is for players to inform their partners of the content of their hand. Whilst much of this bidding is often "natural" (describing a hand simply by reference to shape and strength), there is occasional need to resort to conventions which adopt artificial means of imparting very specific information. Bill Root, in his "ABCs of Bridge", defines a convention as "A specific agreement between partners to give an unusual meaning to a bid … "
Conventions are named after their (perceived) author, for example Drury; their promulgator, for example Stayman; or something about the methodology itself, for example the Strong two clubs convention.
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 answers to questions once bidding has begun. Failure to reveal fully the existence and meaning of conventions can be considered an illegal transfer of information between partners.
Perhaps the most widely known and used conventions are Blackwood, which imparts information about the number of aces and kings held; and Stayman which is used to discover a 4-4 fit in a major suit following a no trump bid. It could be argued that takeout doubles are conventional but their usage is so widespread that it is considered a natural bid.
Bridge conventions can be classified according to their purpose:
- Opening bid conventions
- Strong opening bids are used for hands stronger than the "normal" opening bid range (12-20 points in natural systems, 12-15/17 points in artificial systems)
- Weak opening bids are used for hands weaker than the normal opening bid range, but with preemptive value:
- Other opening bid conventions:
- Fit-seeking conventions are used in constructive bidding, in order to find a fit—a suit suitable for trumps
- Slam-seeking conventions are used in constructive bidding so that a partnership can investigate possibility of making a slam (Main article: Slam seeking conventions)
- Defensive conventions or interventions are used to show a specific type of hand after opponents have opened a bidding
- Counter-interventions present a countermeasure after opponents' conventional and natural interventions:
Note: The above list presents an overview and is necessarily incomplete; see the category for a more comprehensive list.
Under the rules of the sponsoring organization (for example national federations such as American Contract Bridge League (ACBL) and the English Bridge Union (EBU), zonal organizations, and the World Bridge Federation (WBF), certain conventions are alertable, the partner of the player making the conventional call must say "alert" (or show an alert card from the bidding box) before the right-hand opponent calls. The right-hand opponent may ask the alerter about the meaning of the convention, or may proceed as usual. If the right-hand opponent does not ask about the convention, their partner may do so when it is their turn. Under ACBL and EBU rules, some conventions are also announced, for example Jacoby transfers. When players makes a transfer bid, their partner must say, "transfer" (or, under EBU rules, state the suit in question).
Sponsoring organizations can require players at all or some levels of competition to have a convention card which is a form completed by the partnership, containing general notes of the system, together with the definition of conventional bids, leads, discards and signals. In ACBL-sanctioned games, all pairs are obliged to have such a card, which must be identical for both members of the partnership. On the ACBL convention card, alertable conventions are shown in red and announceable ones in blue.
Sponsoring organizations may also ban the usage of certain conventions or restrict their use to certain levels of competition, examples are the use of "ambiguous" suits to disrupt opponent's bidding. WBF classifies most "strong pass" and "either-or" methods into so-called HUM (highly unusual methods) and brown sticker conventions, and restricts their usage on WBF-sponsored events. Other zonal and national organizations often do the same. In general, ACBL tends to be more restrictive in allowed usage of conventions than European organizations.