Opener rebids 1NT

Shows a minimum hand, 12-14 HCP. I assume that New Minor Forcing is being played.

Responder's options with a minimum hand (<10):

• Pass
• Return to opener's first suit at the 2-level, such as 1C-1H-1NT-2C (rare)
• Bid a new major at the two level if it's not a reverse. There is only one such auction: 1C/1D-1S-1NT-2H, showing a weak 5-5. Opener can either pass or correct.

Responder's options with an invitational hand:

• Bid 2 of a new minor suit, artificial and forcing for one round (more below); follow with a pass or a non-jump bid
• Bid 2NT showing 11-12 HCP, inviting game if opener is maximum

Responder's options with a game-going hand:

• Bid 2 of a new minor suit, artificial and forcing for one round (more below); follow with a jump bid
• Bid 3NT
• Bid a new suit at the 2 level when it's a reverse (e.g., 1C-1H-1NT-2S showing 4-5 in the majors and forcing to game)
• Jump in new suit (e.g., 1C-1H-1NT-3D)
• Jump rebid (e.g., 1C-1H-1NT-3H)
• Jump raise (e.g., 1C-1H-1NT-3C)

Note that all jumps are game forcing; use NMF without a jump to create an invitational sequence.

New Minor Forcing

Promises at least invitational values, and asks opener to show 3-card support for responder's major or to show a previously unbid 4-card heart suit. It does not promise anything in the suit bid (with one exception: if the auction started 1H-1S-1NT, responder should make his NMF call in the better minor. The sequence tends to imply a stopper, although it's still considered artificial and alertable).

Opener's actions:

• With a maximum hand opener can make a jump rebid, which is forcing to game.
• If opener's rebid is at or below 2NT it is not forcing.

Responder's possible follow-ups with invitational values:

• Pass (if opener's bid was at or below 2NT)
• Rebid the minor at the 3 level (e.g., 1C-1H-1NT-2D-2NT-3D) to show a 2-suited hand.
• Bid a new major at the 3-level. This shows an invitational hand that's 5-5 in the majors, e.g., 1C-1S-1NT-2D-2NT-3H)

Responder's possible actions with game-going values:

• Place the contract, e.g., 3NT, 4 of a major
• Make a jump bid to establish a game force

Opener makes a minimum rebid in a new suit (e.g., 1C-1H-1S)

Opener's sequence is not forcing but his hand is limited only by his failure to jump shift. He can therefore have up to about 19 points.

Responder's options with a minimum hand:

• Pass
• Give preference to opener's first suit
• Rebid responder's first suit at the two level. This shows a weak hand with a single long suit of 6+ cards.
• Bid 1NT
• Bid 1S. The sequence 1C-1D-1H-1S is alertable if the partnership is playing Fourth Suit Forcing, since it might not be a real suit. It's forcing for one round only so it can be made with a minimum.

With invitational or game-going hands, the meaning of various bids depends on whether the partnership is using Fourth Suit Forcing and in which form (FSF can be played as either a one-round force or a game force). If FSF is a game force then most jump bids become invitational; if FSF is a one-round force then most jump bids become game forcing. The basic idea behind both treatments is that there has to be a way to bid every hand type.

Fourth suit forcing - definition

Fourth suit forcing applies only to responder's second bid when no other force is in effect, i.e., when opener hasn't reversed or jump shifted, and when responder's first bid was not a 2/1 game force. It is off in competition (but see below).

When playing FSF to game

Responder's rebid options with an invitational hand:

• Jump raise one of opener's suits (1C-1H-1S-3S)
• Jump rebid responder's own suit (1C-1H-1S-3H)
• Bid 2NT
• Bid 1S (the sequence 1C-1D-1H-1S is never game forcing)

Responder's rebid options with a game-going hand:

• Bid the 4th suit
• Bid game directly

When playing FSF for one round

Responder's rebid options with an invitational hand:

• Bid 2NT (could be either 11-12 HCP or an invitational 2-suiter including the unbid suit)
• Bid the 4th suit

  If opener's response to the FSF bid is at or below 2NT it is not forcing; otherwise it is forcing to game (Root and Pavlicek).

Responder's rebid options with a game-going hand:

• Jump raise in one of opener's suit (1C-1H-1S-3S)
• Jump rebid responder's own suit (1C-1H-1S-3H)
• Bid 3NT
• Bid the 4th suit and continue with a jump
• Jump in the 4th suit (natural, shows 5-5 and game values)

My own question: Root and Pavlicek say that FSF is off in competition. This certainly makes sense when one of the opponents has overcalled, since a bid of the 4th suit is now a cue bid. Two questions that I can't answer right now: What happens when the only interference has been a takeout double? If FSF is off, what happens to the rules in this section about forcing versus invitational jump bids? Do all jumps become invitational, with a cue bid being the only possible game force? This same question applies to the next section as well.

Opener rebids his original minor (e.g., 1D-1S-2D)

This sequence is difficult to handle since the Fourth Suit Forcing option isn't available. It gets very sketchy treatment in most books, but Goren's New Bridge Complete (1980 edition) contains some useful information.

Opener can be expected to have a 6-card suit and <15 HCP.

Responder's options with a minimum:

• Pass
• Rebid responder's original suit at the 2-level, showing a 6+ card suit and no tolerance for opener's suit

Responder's options with an invitational hand:

• 2NT, promising stoppers
• A new suit, forcing for one round
• Jump rebid in a major (1D-1S-2D-3S). This is NOT forcing.

Responder's options with a game-going hand:

• 3NT
• A new suit, forcing for one round; in a pinch this can be made on a 3-card suit since responder intends to keep bidding.
• Jump in a new suit (game force)
• Jump rebid in a minor (1C-1D-2C-3D). This is game forcing; note that the equivalent sequence in a major is only invitational.

Opener makes a jump rebid in his original suit (e.g., 1D-1S-3D)

Opener's sequence is not forcing, but if responder makes any bid then a game force is established (Goren).

Opener jumps to 2NT (e.g., 1D-1S-2NT)

Opener's sequence is not forcing, but if responder makes any bid then a game force is established (Goren).

Opener reverses (e.g., 1D-1S-2H)

Definition of a reverse

Everyone agrees that 1D-1S-2H is a reverse, but there is less consensus when responder's first bid was at the two level. One useful agreement is that after the specific sequence 1D-2C, opener can bid either major without promising extras.

A reverse by opener is a one-round force, and the auction may not stop below 3 of the opener's original suit. With a minimum hand (<8 pts) responder bids 2NT; any other bid by responder is forward-going and establishes a game force (this is Goren's treatment).

Opener makes a jump rebid in a new suit (e.g., 1D-1S-3C)

Opener's sequence is forcing to game and shows 19+ points.

Responder's jump shift

A murky area that requires partnership discussion. There are several options presented in various books, all dramatically different.

• If playing a 2/1 game forcing system, a jump shift ought to show a hand with either (1) a self-sufficient suit or (2) support for opener's suit with slam interest. With this understanding there is no precise high-card point requirement.
• The traditional Standard American approach is that a jump shift shows about 19+ points and is almost a slam force.
• Root (Common Sense Bidding) suggests an intermediate treatment where the JS shows 16-18 points. That allows opener to make a slam exploration if he has extras, or to sign off in game with a minimum.

Sources:

Goren's New Bridge Complete, 1980 Edition.  This edition includes 5-card majors and 2/1 forcing.

Root's Common Sense Bidding

Root and Pavlicek's Modern Bridge Conventions

Bergen's Better Bidding with Bergen, Vol 1