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Acol is the bridge bidding system that, according to The Official Encyclopedia of Bridge, is "standard in British tournament play and widely used in other parts of the world". It is a natural system using four-card majors and, most commonly, a weak no trump.
Polish Club is a bridge bidding system which was developed in Poland, where it is the most popular bidding system, and which is also used by players of other countries. It is a type of small club system.
The forcing notrump is a bidding convention in the card game of bridge.
In the card game of bridge, the unusual notrump is a conventional overcall showing a two-suited hand. It was originally devised by Al Roth in 1948 with Tobias Stone, to show the minor suits after the opponents opened in a major.
Zar Points (ZP) is a statistically derived method for evaluating contract bridge hands developed by Zar Petkov. The statistical research Petkov conducted in the areas of hand evaluation and bidding is useful to bridge players, regardless of their bidding or hand evaluation system. The research showed that the Milton Work point count method, even when adjusted for distribution, is not sufficiently accurate in evaluating all hands. As a result, players often make incorrect or sub-optimal bids. Zar Points are designed to take many additional factors into consideration by assigning points to each factor based on statistical weight. While most of these factors are already implicitly taken into account by experienced players, Zar Points provides a quantitative method that allows them to be incorporated into bidding.
Preempt is a bid in contract bridge whose primary objectives are (1) to thwart opponents' ability to bid to their best contract, with some safety, and (2) to fully describe one's hand to one's partner in a single bid. A preemptive bid is usually made by jumping, i.e. skipping one or more bidding levels. Since it deprives the opponents of the bidding space, it is expected that they will either find a wrong contract of their own, or fail to find any. A preemptive bid often has the aim of a sacrifice, where a partnership bids a contract knowing it cannot be made, but assumes that, the penalty will still be smaller than the value of opponents' bid and made contract.
The weak two bid is a common treatment used in the game of contract bridge, where an opening bid of two diamonds, hearts or spades signifies a weak hand with a long suit. It is used in combination with the strong two clubs bid and is a form of preemptive bid. The term refers to an opening bid, and is not to be confused with the "weak jump overcall", which denotes a similar type of hand, but is bid over an opponent's opening bid.
In the card game contract bridge, a takeout double is a low-level conventional call of "Double" over an opponent's bid as a request for partner to bid his best of the unbid suits. The most common takeout double is after an opponent's opening bid of one of a suit where the double shows a hand with opening values, support for all three unbid suits and shortness in the suit doubled. Normally, the partner of the doubler must bid his best suit but may pass if (a) his right hand opponent intervenes or (b) on the more rare occasions when his hand is such that he wishes to convert the takeout double to a penalty double.
Cappelletti is a bridge bidding convention for the card game contract bridge, primarily used to interfere over opponent's one notrump (1NT) opening. Usually attributed to Michael Cappelletti and his longtime partner Edwin Lewis, origin of the concept is also claimed by Fred Hamilton, John Pottage and Gerald Helms.
Landy, named after its inventor Alvin Landy is the first of several conventional defenses created to compete against an opponent's one notrump (1NT) opening. Landy is a 2♣ overcall of the opponents' 1NT opening to show at least four cards in each of the major suits; all other bids are natural. Requirements for the overcall vary from partnership to partnership: some require 5-5, some 5-4, and yet others only 4-4. The partner can take a preference to either major or make a non-forcing bid of a suit; 2NT is used as a forcing query.
Multi 2 diamonds, or simply Multi, is a contract bridge convention whereby the opening bid of 2♦ shows multiple types of hands, which always includes a weak-two bid in either major suit, while the additional meaning may be a strong balanced hand, or a 20-22 three suiter. The inherent ambiguity as to both suit and strength makes it a powerful and popular convention capable of seriously disrupting the opponents' bidding.
Rubinsohl is a bridge convention that can be used to counter an opponent's intervention over a 1NT opening bid. After opponent's two-level overcall, all bids starting from 2NT are transfer bids to the next strain.
Lionel is a contract bridge bidding convention used in defense against an opposing 1NT openings. Using Lionel, over a 1NT opening of the opponents:
In the card game bridge, CoCa or Comfy Canapé is a conventional defense against opposing 1NT openings. When playing CoCa, over a 1NT opening of the opponents, both a double as well as a 2♣ overcall are conventional and establish spades and hearts, respectively as anchor suits. Higher overcalls can be either natural, or conventional.
OKbridge 2/1 is a duplicate bridge bidding system combining two-over-one game-forcing and Walsh bidding methods.
Astro is a contract bridge bidding convention used to intervene over an opponent's one notrump (1NT) opening bid. The name is derived from the initials of the surnames of its inventors - Paul Allinger, Roger Stern and Lawrence Rosler.
Mylläri is a bridge convention used to intervene over opponents' 1NT opening. Typically it only applies if the opponents are using a strong 1NT opening. Its invention is attributed to Jay Barron and is named after Finnish Bridge player Maria Mylläri.
