Bidding systems and conventions

A bidding system is a set of partnership agreements on the meanings of bids. A partnership's bidding system is usually made up of a core system, modified and complemented by specific conventions (optional customizations incorporated into the main system for handling specific bidding situations) which are pre-chosen between the partners prior to play. The line between a well-known convention and a part of a system is not always clear-cut: some bidding systems include specified conventions by default. Bidding systems can be divided into mainly natural systems such as Acol and Standard American, and mainly artificial systems such as the Precision Club and Strong Diamond (see Strong Diamond). Calls are usually considered to be either natural or conventional (artificial). A natural bid is one in which the suit and level bid is essentially passing the information "I have some cards in this suit and (usually) some high cards in my hand"; a natural double says in effect "I don't think the opponents can make their contract, so I want to raise the stakes". By contrast, a conventional (artificial) call offers and/or asks for information by means of pre-agreed coded interpretations, in which some calls convey very specific information or requests that are not part of the natural meaning of the call. Thus in response to 4NT, a 'natural' bid of 5 would state a preference towards a diamond suit or a desire to play the contract in 5 diamonds, whereas if the partners have agreed to use the common Blackwood convention, a bid of 5 in the same situation would say nothing about the diamond suit, but tell the partner that the hand in question contains exactly one ace. Conventions are valuab e in bridge because of the need to pass information beyond a simple like or dislike of a particular suit, and because the limited bidding space can be used more efficiently by taking situations in which a given call will have less utility, because the information it would convey is not valuable or because the desire to convey that information would arise only rarely, and giving that call an artificial meaning that conveys more useful (or more frequently useful) information. There are a very large number of conventions from which players can choose; many books have been written detailing bidding conventions. Well-known conventions include Stayman (to ask for the showing of any 4 card major suit in a 1NT opener's hand), Jacoby transfers (a request by the weak hand for the stronger partner to bid a particular suit first, and therefore to become the declarer), and the Blackwood convention (to ask for information on the number of aces and kings held, used in slam bidding situations). The term preempt refers to a high level tactical bid by a weak hand, relying upon a long suit rather than high-value cards for tricks. Preemptive bids serve a double purpose they allow players to indicate they are bidding on the basis of a long suit in an otherwise weak hand, which is important information to share, and they also consume substantial bidding room before a possibly strong opposing pair can identify whether they have a good possibility to play the hand, or in what suit or at what level they should do so. Several systems include the use of opening bids or other early bids with weak hands including long (usually six to eight card) suits at the 2, 3 or even 4 or 5 levels as preempts.