Negative free bid


Negative free bid is a contract bridge treatment whereby a free bid by responder over an opponent's overcall shows a long suit in a weak hand and is not forcing. This is in contrast with standard treatment, where a free bid can show unlimited values and is unconditionally forcing. The treatment is a relatively recent invention, and has become quite popular, especially in expert circles.
Negative free bids resolve relatively frequent situations where the responder holds a long suit with which he would like to compete for a partscore, but is deprived from bidding it by opponent's overcall.

Example

For example, if South holds: , partner opens 1 and East overcalls 1, he couldn't bid 2 in standard methods, as it would show 10+ high-card points, and a negative double would be too off-shape. With NFB treatment in effect though, he can bid 2 which the partner may pass.
However, as a corollary, negative free bids affect the scope of negative double; if the hand is suitable for "standard" forcing free bid, a negative double has to be made first and the suit bid only in the next round. Thus, the negative double can be made with the following types of hand:
This can sometimes allow the opponents to preempt effectively.
WestNorthEastSouth
11Dbl4
?

For example, West, holding:, after this auction is in an awkward situation — he doesn't know whether partner has spades or not; whether South was bidding to make or to sacrifice — is it correct to double, bid 4 or pass?