The “second negative” is also called the “double negative.” Don’t confuse it with the “negative double” – they are totally different bids.
Partner opens 2♣
When partner opens 2♣ and you have a crummy hand, you first respond 2♦. This is just a negative bid, showing 0 to 7 points. But if you are truly dreadful, you need to turn partner off from his lofty dreams by giving him a “second negative.”
This is an important convention that comes in handy.
Responder’s Second Bid
Modern bidding has a problem-child:
♠ Q 8 7 North South
♥ A Q 9 8 7 1♦ 1♥
♦ K J 6 1♠ ??
♣ 5 4
South has a problem: He wants to bid NT, but not without a stopper in clubs, the only unbid suit. He should not jump in his 5-card heart suit (only perverts do that), and he should not raise opener’s second suit with only 3-card support. There is a nice solution to this dilemma:
After a 2/1 response, opener can bid a new 4+ card suit (not 3 cards) on the 2-level, so responder should raise the new suit with 4-card support. With less support, try NT, or rebid a 6+ card suit, or bid the fourth suit (artificial – called "Fourth Suit Forcing") to get more information from opener.
Your partner opened the bidding and you gave him a game-forcing 2/1 response. Now it is your second bid and you are responsible for placing the final contract. You have all the information (two bids from opener), so you decide.
If you have 3-card support for opener's major, now is the time to show it.
You have opened the bidding and your beautiful partner bid a new suit on the two-level. This 2/1 response is forcing to game. Opener describes the shape of his hand. Extra strength can be shown later. Your options are as follows:
This is the crown jewel of the system. 2/1 (read Two-over-One) refers to responder’s first bid of a new suit on the two-level. In Standard American it shows 11+ points (or a good 10). Now, most of the bridge world plays it as a game-forcing bid, at least 13+ points (or a good 12). The advantage is simple: by telling the opener immediately that the hand is good enough for game, the partnership has plenty of room to explore the best contract without jumping needlessly. Note: Game level is defined as 3 NT or 4 of a suit. If your trump suit is a minor, you are not forced all the way to 5♣ or 5♦. Even if you've made a 2-over-1 response, your auction can end at 4♣ or 4♦ if that's your agreed suit.
With 13-16 Points and 4-Card Support Many advocates of the 2/1 system use the "Jacoby 2 NT Forcing Raise" and "Splinter Raises". Jacoby 2 NT Forcing Raise: • 4+ card support • 13+ support points • no void, no singleton