Acol is the bridge

Contract bridge

Contract bridge, usually known simply as bridge, is a trick-taking card game using a standard deck of 52 playing cards played by four players in two competing partnerships with partners sitting opposite each other around a small table...

 bidding system that, according to The Official Encyclopedia of Bridge

The Official Encyclopedia of Bridge

The Official Encyclopedia of Bridge presents comprehensive information on the card game contract bridge with limited information on related games and on playing cards...

, is "standard in British tournament play and widely used in other parts of the world". It is named after the Acol Bridge Club, previously located on Acol Road in London

London

London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...

 NW6, where the system started to evolve in the late 1920s. According to Terence Reese

Terence Reese

John Terence Reese was a British bridge player and writer, regarded as one of the finest of all time in both fields...

, its main devisers were Maurice Harrison-Gray

Maurice Harrison-Gray

Maurice Harrison-Gray , known always as 'Gray', was an English professional contract bridge player. For about thirty years from the mid-thirties to the mid sixties he was one of the top players, and won the European Championship four times - in 1948, 1949, 1950 and 1963.- Life :Gray was the child...

, Jack Marx

Jack Marx (bridge)

Jack Marx was a British international bridge player who was instrumental in developing the Acol System of bidding.- Life :Marx went to Repton School, and served as a Captain in World War II in the RASC....

 and S. J. Simon

S. J. Simon

S.J. "Skid" Simon was a British author and bridge player. From 1937 until his death he collaborated with Caryl Brahms on a series of comic novels and short stories, mostly with a background of ballet or of English history...

. Marx himself, writing in the Contract Bridge Journal in December, 1952, said: "...the Acol system was pieced together by Skid Simon

S. J. Simon

S.J. "Skid" Simon was a British author and bridge player. From 1937 until his death he collaborated with Caryl Brahms on a series of comic novels and short stories, mostly with a background of ballet or of English history...

 and myself the best part of 20 years ago." In another account, Marx and Simon...
The first book on the system was written by Ben Cohen and Terence Reese. Skid Simon explained the principles that lay behind the system, and the system was further popularised in Britain by Iain Macleod

Iain Macleod

Iain Norman Macleod was a British Conservative Party politician and government minister.-Early life:...

. The Acol system is continually evolving but the underlying principle is to keep the bidding as natural as possible and preferring to bid a suit over notrump whenever possible. It is common in the British Commonwealth

Commonwealth of Nations

The Commonwealth of Nations, normally referred to as the Commonwealth and formerly known as the British Commonwealth, is an intergovernmental organisation of fifty-four independent member states...

 but rarely played in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

.

Bidding system structure

As a bidding system, Acol has the following characteristics:

• It is a natural system: most opening bids, responses and rebids are made with at least 4 cards in the suit bid, and most no trump bids are made with balanced hands.
• It is a four-card major system: only four-card suits are required to open 1 or 1, unlike Standard American
  Standard American
  Standard American is a common bidding system for the game of bridge in the United States, also widely used in the rest of the world. This system, or a slight variant, is learned first by most beginners in the U.S. and may be referred to as 'Goren'; a dominant version used in on-line computer...
  
   and many other systems where five-card suits are typically required.
• It is an approach forcing system: whether or not a bid is forcing (systemically requiring a response) depends on the previous bidding ("approach"). This is in contrast to level forcing systems, such as 2-over-1
  2/1 game forcing
  2/1 game forcing is a bidding system in modern contract bridge in which, after a one-level opening bid, a non-jump response in a new suit at the two level commits the partnership to bidding at least game....
  
  , where the level of the bid determines whether or not it is forcing.
• It makes extensive use of limit bids: limit bids describe the hand so closely, in terms of high card points (HCP) and shape, that the one who makes the limit bid is expected to pass on the next round, unless partner makes a forcing bid.
• Understanding and correct use of limit bids and forcing bids is fundamental to applying the system: all no trump bids below the level of 4NT are limit bids, as are all suit bids that merely repeat a suit already bid by the partnership; changes of suit may be forcing or not depending on the approach bids.
• The level of the 1 NT opening bid influences other bids: the normal choice is between a "weak no trump" (12-14 HCP) and a "strong no trump" (15-17 HCP).

Variants

Acol is an unregulated system. There is no Acol governing body and no single publication containing the "official" Acol (unlike, for example, Standard American

Standard American

Standard American is a common bidding system for the game of bridge in the United States, also widely used in the rest of the world. This system, or a slight variant, is learned first by most beginners in the U.S. and may be referred to as 'Goren'; a dominant version used in on-line computer...

 Yellow Card). It can be compared to a living language since it is liable to change at the whim of users. The main versions of Acol in use today are:

• Acol: unregulated Acol, from the simple to the complex, remains in common use throughout the UK. At any one time the version in most common use will be known as "Standard Acol" although this term will mean different things to different players and is becoming increasingly confused with Standard English Acol.
• Standard English Acol (originally called simply "Standard English"). Developed by Sandra Landy under the auspices of the English Bridge Union
  English Bridge Union
  The English Bridge Union or EBU is a player-funded organisation that promotes and organises the card game of duplicate bridge in England. It has an office in Aylesbury with a staff of more than twenty people...
  
   (EBU), this variant was designed to facilitate the learning of bridge and to provide standardised guidance to novices, intermediate players and their teachers. This variant uses the weak 1NT opening (12-14 points). Simple conventions such as Stayman, Blackwood
  Blackwood convention
  In the partnership card game contract bridge, the Blackwood convention is a popular bidding convention that was developed by Easley Blackwood. It is used to explore the partnership's possession of aces, kings and in some variants, the queen of trumps, to judge more precisely whether slam is likely...
  
   and Transfers are included at various stages in the learning process. It has been widely promulgated by the EBU and by EBUTA in particular, but the exact form is used mainly by those who have learned their bridge recently and those who taught them.
• Benjaminised (Benji) Acol: recognising that strong 2 opening bids are rarely used, the 2 and 2 openings are used to show weak hands containing long suits (under 10 HCP and a 6-card suit). Very strong hands (8 playing tricks
  Hand evaluation
  In contract bridge, various bidding systems have been devised to enable partners to describe their hands to each other so that they may reach the optimum contract. Key to this process is that players evaluate and re-evaluate the trick-taking potential of their hands as the auction proceeds and...
  
  ) are shown by an opening bid of 2 which forces a 2 response allowing suits to be shown. The strongest hands (e.g., 23+ points or a game force hand) are shown by an opening bid of 2.
• Reverse Benji: identical to Benji except that the 2 and 2 bids are switched in meaning. A 2 opening bid is now the strongest bid as in basic Acol.
• Acol with Three Weak Twos: this variant is similar to Reverse Benji Acol except that the strong 2 bid is abandoned in favour of a third weak two (in diamonds). Thus 2 is the only strong bid in this system. Abandoning the extra grade of strong bid means that 'Acol two' style hands cause some problems, either having to be opened at the one level or forced into the 2 bid.
• Acol with Multi 2: this variant of Acol makes use of the Multi 2 diamonds
  Multi 2 diamonds
  Multi or Multi 2 diamonds is 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...
  
   convention. The 2 bid is used as in standard Acol (23+ points). Various uses are made of the 2 and 2 bids, with traditional strong twos or Lucas twos being some popular methods.

Opening bids

Opening bids promise at least 12 high card points (HCP), or the equivalent in HCP and shape, unless preempt

Preempt

Preempt is a bid in contract bridge whose primary objectives are to thwart opponents ability to bid to their best contract, with some safety, and 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...

ing. Apart from NT, opening bids guarantee the ability to make a rebid over any forcing response from partner. There are six special opening bids which are quite closely defined, and one wide-ranging opening bid:

• Special opening bids:
  • 1 NT - Shows a balanced hand (4-3-3-3, 4-4-3-2 or 5-3-3-2). Subject to partnership agreement, it may be either weak (12-14 HCP), strong (15-17 or 16-18 HCP) or variable (i.e., varying between weak and strong according to vulnerability). Limit bid.
  • 2 - Conventional game-forcing bid, promising game-going values (normally 23+ HCP) and at least 5 quick tricks. Game forcing unless responder replies 2 and opener rebids 2NT.
  • 2 of any other suit - Strong two bid
    Strong two bid
    In contract bridge, a strong two-bid is an opening bid of two in a suit. i.e. 2, 2, 2 or 2 . It is a natural bid, used to show a hand that is too strong to open at the one level – more than about 21 points...
    
     which shows a strong hand with at least eight playing tricks and a 6-card suit (or two 5-card suits). Forcing for one round.
  • 2NT - Shows a balanced hand with 20-22 HCP. Limit bid.
  • 3 of a suit - Pre-emptive, normally seven or more cards in the suit bid (may be six at favourable vulnerability), weak hand (not more than 10 HCP). Not forcing.
  • 3NT - Pre-emptive, shows a long solid minor suit and is called the Gambling 3NT
    Gambling 3NT
    Gambling 3NT is a preemptive opening bid. The bid is used to describe a hand containing a minor suit of at least 7 cards in length and headed by the AKQ at minimum...
    
    
• Wide-ranging opening bid (made if too strong to pass and unable to make one of the special opening bids):
  • 1 of a suit - Promises a minimum of 12 HCP and a 4-card suit, 11 HCP and a 5-card suit, or 10 HCP and a 6-card suit. Not forcing.

Responses to 1 of a suit

• pass - less than 6 HCP
• 2 of opener's suit - at least four-card support and 6-9 HCP. Limit bid.
• 3 of opener's suit - at least four-card support and 10-12 HCP. Invites game if opener has requisite strength (14 HCP or more). Limit bid.
• 4 of opener's suit - at least five-card support for opener's major and 6-10 HCP, this is pre-emptive and to play.
• 1 NT - 6-9 HCP, denies ability to bid at 2 level. Not necessarily balanced. Limit bid.
• 2 NT - balanced, 10-12 HCP. Limit bid.
• 3 NT - balanced, 12-15 HCP. Limit bid.
• 1 of a new suit - promises at least four cards in the suit bid, 6 HCP upwards. Forcing for one round.
• 2 of a new suit (below 2 of opener's suit) - normally 5-card suit, at least a good 8 or 9 HCP. Forcing for one round
• Jump in a new suit - 5-card suit (or support for partner), at least 16 HCP, Game force.

note: these last three bids may conceal 4-card support for opener's suit, whereas the three NT responses deny 4-card support for opener

Responses to 1 NT

• 2 - Stayman. Opener responds 2 with no four-card major, 2 with a four-card heart suit and 2 with four spades (denies four hearts). Forcing for one round.
• 2 of any other suit - weak takeout, opener must pass. Some players make use of transfers
  Jacoby transfer
  The Jacoby transfer, or simply "transfers", in the card game contract bridge, is a convention initiated by responder following partner's notrump opening bid that requests opener rebid in the suit ranked just above that bid by responder, i.e...
  
  .
• 3 of a suit - shows a five-card suit, forcing for one round.
• 2NT - 11-12 HCP. invites game if opener is maximum (i.e., for a weak opening NT, if opener has 14 or a good 13 HCP).
• 3NT - to play.
• 4 - asks for aces. (Gerber
  Gerber convention
  Gerber is a contract bridge convention devised by Dr. William Konigsberger and Win Nye from Switzerland who published it in 1936; John Gerber of Texas introduced it to North America in 1938 where it was named after him...
  
  )
• 4, 4 - to play.
• 4NT - slam invitation, opener bids 6NT with a maximum.
• 5NT - slam invitation, opener bids 6NT unless a minimum. Note: some play as invitation to 7NT; opener bids 6NT if minimum, 7NT with a maximum).

Responses to 2 NT

• 3 - Baron
  Baron convention
  Baron is a set of conventions in the game of contract bridge. There are three common variations of the Baron convention used in the game.-Baron Three Clubs:...
  
  . Opener bids his lowest four-card suit. Forcing. (Stayman may also be used as in responses to 1NT; i.e., 3 shows no 4-card major).
• 3 of other suit - shows a five card suit, forcing to game.
• Other responses as over 1NT.

Responses to 2

• 2 - negative. Responder lacks the strength for a positive response. Unless opener rebids 2NT (balanced, 23-24 HCP, which may be passed), the sequence is forcing to game.
• 2NT - fairly balanced, 8 or more HCP. Forcing to game.
• 2 of a suit - at least five in the suit, the equivalent of an ace and a king in high cards. Forcing to game.
• 3 of a suit - Solid suit of at least six cards. Forcing to game.

Responses to 2 of a suit

• 2NT - negative. Responder lacks the strength for a positive response.
• Simple bid of a new suit - 8 or more HCP, at least five in the suit. Forcing to game.
• 3 of opener's suit - 5-8 HCP, at least 3-card support. Forcing to game.
• 3NT - flat hand, 8-11 HCP. Not forcing.

Opener's suit rebid after one-level opening

Rebid own suit

• Rebid of own suit at lowest level - minimum hand, at least a five-card suit, 12-15 HCP, non-forcing.
• Jump rebid of own suit - strong hand, normally at least six-card suit, 15-19 HCP, non-forcing but highly invitational.

Bid new suit

• Bid of new suit at lower level than first suit - minimum hand, 12-15 HCP, first suit has at least as many cards as second suit, non-forcing.
• Bid of new suit at higher level than two of the first suit, but without jumping (a Reverse bid
  Reverse (bridge)
  A reverse, in the card game contract bridge, is a bidding sequence designed to show additional strength without the need to make a jump bid; specifically two suits are bid in the reverse order to that expected by the basic bidding system. Precise methods and definitions vary with country and...
  
  ) - strong hand, 16-19 HCP, first suit has more cards (at least five) than second suit, forcing for one round.
• Jump in new suit - strong hand, 16-19 HCP, first suit has at least as many cards as second suit, forcing for one round.

Support for responder

• Simple raise of responder's suit - minimum hand, 4-card support, 12-15 HCP, non-forcing
• Jump raise of responder's suit - stronger hand, 4-card support, 16-18 HCP, non-forcing
• Jump to game in responder's suit - game values, 4-card support, 19 HCP, non-forcing

Opener's NT rebid after one-level opening

(The following bids assume a weak NT opening)

After suit response at one level the traditional rebids are:

• 1NT - balanced, 15-16 HCP, limit bid
• 2NT - balanced, 17-18 HCP, limit bid
• 3NT - balanced, 19 HCP, limit bid

However, the modern approach modifies the ranges for the rebids thus:

• 1NT - balanced, 15-17 HCP, limit bid
• 2NT - balanced, 18-19 HCP, limit bid
• 3NT - Often an Acol two type of hand prepared to play in NT.

After a suit response at two level the traditional rebids are:

• 2NT - balanced, 15-17 HCP, limit bid
• 3NT - balanced, 18-19 HCP, limit bid

The modern approach is to use the 2NT rebid as forcing and use 3NT as 15-17 with support for the minor that responder has bid (one option).

After the 2NT (forcing) rebid, either bid naturally or use an enquiry (3) to seek definition of the 2NT rebid.

Fourth suit forcing

A bid of the fourth suit at the 2 level by responder is a one-round force, usually asking opener to bid no trumps with a stopper in the fourth suit. A fourth suit bid at the 3 level is similar, but forcing to game.