Semiforcing 1NT

The 1NT response to a major opening is semiforcing. The semiforcing 1NT is a dustbin for hands with 6~11 HCP and no other available bid. However, with a flat hand, 3-card support, and exactly 6 or 11 HCP, it is better to bid 1NT instead of direct support.

In Wbridge5, the 1NT is more forcing than an American semiforcing 1NT.

• Opener always rebids 2♣ with 3 cards if balanced.
• A 4-card lower-ranking side suit is never passed by suit quality.

Flat raises

The 4-3-3 side suits make it awkward to play a suit contract. The original raise system brings things too far with 6 and 11 HCP flat raises. We should back off by bidding 1NT to guide opener better.

Such 1NT is a bet on opener's usual rebidding. Opener's rebid provides good continuations like forcing 1NT. Opener's pass leads to a mediocre but acceptable result. Wbridge5 requires opener with 3 clubs to bid to dissuade opener from passing.

Flat weak raise

Try to sign off in 2M.

With flat 6 HCP, simple support may lead to disastrous 1M-2M; 3m-3M. Since 2M is usually the best contract and 1NT is no worse than 3M, bid 1NT and hope opener not pass.

Flat limit raise

Invite minimum opener in the next round.

Our special 2NT enforces major fit and never results in a notrump contract. Bid 1NT to let opener reconsider notrump contracts.

When does opener pass

As usual, opener passes when no bid describes. However, we try hard to bid, so there are only few hands left for the pass.

Minimum balanced hands with doubleton clubs

The other 2/3 balanced hands are safely biddable.

Flannery opening hands with no biddable minor

These 4=5=2=2 and 4=5=3=1 hands are inherently hard to bid.

Opener's rebids

Choice of strain

Notrump vs suit

Major > notrump > minor

Original suit vs side suit

7-card original suit > 4-card side suit > 6-card original suit > 3-card 2♣

After 1♥-1NT

2♣

13~18 points, 3+ cards.

2♦

13~18 points, 4+ cards.

2♥

13~18 points, 6+ cards.

2♠

18~21 points, 4+ cards.

2NT

17~18 HCP, no void nor singleton.

3♣, 3♦

19~21 points, 4+ cards.

3♥

19~21 points, 6+ cards.

3NT

19~21 HCP, no void nor singleton.

After 1♠-1NT

2♣

13~18 points, 3+ cards.

2♦, 2♥

13~18 points, 4+ cards.

2♠

13~18 points, 6+ cards.

2NT

17~18 HCP, no void nor singleton.

3♣, 3♦, 3♥

19~21 points, 4+ cards.

3♠

19~21 points, 6+ cards.

3NT

19~21 HCP, no void nor singleton.

Second responses to an 1♠ opener

These 1♠ continuations are mentioned first to derive 1♥ counterparts because this way is easier than vice versa. Both bids in 1♠-1NT contain more shapes than in 1♥-1NT. Derivation of 1♥ rules from 1♠ ones is simple generalization except opener's reverse.

After 1♠-1NT; 2♣

2♦, 2♥

Constructive, 5+ cards, 8~11 HCP if only 5 cards.

2♠

Preference, usually 2~3 cards.

2NT

Invitational, 9~11 HCP.

3♣

Invitational, 9~11 points, 5+ cards.

3♠

Flat limit raise, 11 HCP, 3 cards with 4-3-3 side suits.

After 1♠-1NT; 2♦

2♥

Constructive, 5+ cards, 8~11 HCP if only 5 cards.

2♠

Preference, usually 2~3 cards.

2NT

Invitational, 9~11 HCP.

3♣

6+ cards.

3♦

Invitational, 9~11 points, 4+ cards.

3♠

Flat limit raise, 11 HCP, 3 cards with 4-3-3 side suits.

After 1♠-1NT; 2♥

2♠

Preference, usually 2~3 cards.

2NT

Invitational, 9~11 HCP.

3♣, 3♦

6+ cards.

3♥

Invitational, 9~11 points, 4+ cards.

3♠

Flat limit raise, 11 HCP, 3 cards with 4-3-3 side suits.

After 1♠-1NT; 2♠

2NT

Invitational, 9~11 HCP, 0~2 spades.

3♣, 3♦, 3♥

Intolerance to 2♠, 6+ cards.

3♠

Invitational, 9~11 points, 2~3 cards.

Second responses to an 1♥ opener

Most responses can be deduced from 1♠ continuations. This section lists only discrepancies. There are 2 sources of discrepancies, both related 2♠.

• Opener has reverse 2♠.
• Responder denied spades, which makes 2♠ good for a forcing convention.

After 1♥-1NT; 2♣

2♠!

Super invitation, 9~11 HCP, 5+ clubs, stopper in spades.

After 1♥-1NT; 2♦

2♠!

Super invitation, 9~11 HCP, 4+ diamonds, stopper in spades.

After 1♥-1NT; 2♥

2♠!

Super invitation, 9~11 HCP, 2+ hearts, balanced with stopper in spades.

Comparison to other 1NT treatments

I think that Wbridge5's 1NT is an eligible semiforcing 1NT because 2♣ rebid is more frequent than pass. Naming of American semiforcing 1NT is questionable because pass is still the most frequent call. Such 1NT should be called nonforcing instead.

The following is analysis after a minimum opening.