In its basic format, it is played by four players in two competing partnerships,[1] with partners sitting opposite each other around a table.

[a] Millions of people play bridge worldwide in clubs, tournaments, online and with friends at home, making it one of the world's most popular card games, particularly among seniors.

The deal is scored based on the number of tricks taken, the contract, and various other factors which depend to some extent on the variation of the game being played.

The French physician and author Rabelais (1493–1553) mentions a game called "La Triomphe" in one of his works, and Juan Luis Vives's Linguae latinae exercitio (Exercise in the Latin language) of 1539 features a dialogue on card games in which the characters play 'Triumphus hispanicus' (Spanish Triumph).

The first known rule book for bridge, dated 1886, is Biritch, or Russian Whist written by John Collinson, an English financier working in Ottoman Constantinople.

It and his subsequent letter to The Saturday Review, dated 28 May 1906, document the origin of Biritch as being the Russian community in Constantinople.

[8] Biritch had many significant bridge-like developments: dealer chose the trump suit, or nominated his partner to do so; there was a call of "no trumps" (biritch); dealer's partner's hand became dummy; points were scored above and below the line; game was 3NT, 4♥ and 5♦ (although 8 club odd tricks and 15 spade odd tricks were needed); the score could be doubled and redoubled; and there were slam bonuses.

[19] To illustrate this, the simpler partnership trick-taking game of spades has a similar mechanism: the usual trick-taking rules apply with the trump suit being spades, but in the beginning of the game, players bid or estimate how many tricks they can win, and the number of tricks bid by both players in a partnership are added.

Players take turns to call in a clockwise order: each player in turn either passes, doubles – which increases the penalties for not making the contract specified by the opposing partnership's last bid, but also increases the reward for making it[20] – or redoubles, or states a contract that their partnership will adopt, which must be higher than the previous highest bid (if any).

In duplicate bridge the cards are pre-dealt, either by hand or by a computerized dealing machine, in order to allow for competitive scoring.

Once dealt, the cards are placed in a device called a "board", having slots designated for each player's cardinal direction seating position.

There exist many bidding conventions that assign agreed meanings to various calls to assist players in reaching an optimal contract (or obstruct the opponents).

[25] At any time, a player may claim, stating that their side will win a specific number of the remaining tricks.

[44] Overtricks score the same number of points per odd trick, although their doubled and redoubled values differ.

[45] Undertricks are scored in both variations as follows:[24][45] The rules of the game are referred to as the laws as promulgated by various bridge organizations.

The majority of rules mirror those of duplicate bridge in the bidding and play and differ primarily in procedures for dealing and scoring.

This measures relative skill (but still with an element of luck) because each pair or team is being judged only on the ability to bid with, and play, the same cards as other players.

These are placed diagonally across the table, preventing partners from seeing each other during the game; often the screen is removed after the auction is complete.

Well-known conventions include Stayman (to ask the opening 1NT bidder to show any four-card major suit), Jacoby transfers (a request by (usually) the weak hand for the 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 very long suit rather than high cards for tricks.

Most systems use a count of high card points as the basic evaluation of the strength of a hand, refining this by reference to shape and distribution if appropriate.

A natural, or penalty double, is one used to try to gain extra points when the defenders are confident of setting (defeating) the contract.

Standard American, for instance, is a collection of conventions designed to bolster the accuracy and power of these basic ideas, while Precision Club is a system that uses the 1♣ opening bid for all or almost all strong hands (but sets the threshold for "strong" rather lower than most other systems – usually 16 high card points) and may include other artificial calls to handle other situations (but it may contain natural calls as well).

It confirms or passes some information to a partner, and, by implication, denies any other kind of hand which would have tended to support an alternative call.

For example, a bid of 2NT immediately after partner's 1NT not only shows a balanced hand of a certain point range, but also almost always denies possession of a five-card major suit (otherwise the player would have bid it) or even a four card major suit (in that case, the player should use the Stayman convention).

West turns the lead card face up, and the declarer studies the two hands to make a plan for the play.

There is an almost equal chance that it is held by East, in which case it can be trapped against the ace, and will be beaten, using a tactic known as a finesse.

East covers the queen with the king, and South takes the trick with the ace, and proceeds by cashing the remaining master ♣J.

(The trick-by-trick notation used above can be also expressed in tabular form, but a textual explanation is usually preferred in practice, for reader's convenience.

In 2001, the WBF issued a special edition of the lawbook adapted for internet and other electronic forms of the game.