Unusual notrump

In the card game of bridge, the unusual notrump is a conventional overcall showing a two-suited hand. It was originally devised by Al Roth in 1948 with Tobias Stone, to show the minor suits after the opponents opened in a major.

The convention concept is now generally extended to show the "two lowest unbid" suits. Thus, over 1♣, 2NT shows diamonds and hearts; and over 1♦, it shows clubs and hearts. In addition to succinctly describing the hand to the partner, it also deprives the opponents of bidding space, i.e. it has a preemptive effect.

When an opponent opens the bidding with 1♥ or 1♠, the immediate overcall of 2NT shows at least 5-5 in the minor suits (that is, at least five clubs and at least five diamonds) and, presumably, a weak hand (6 to 11 points). If the right hand opponent (RHO) of the partner of the 2NT bid passes, that partner is expected to bid the minor suit that he prefers at the three-level. The unusual notrump extends the principle that when the natural meaning of a bid is not generally very useful, it is profitable to agree that it means something somewhat opposite. That is, while natural notrump bids show a strong hand with balanced distribution, the unusual notrump shows a weak hand with very unbalanced distribution.

If the 2NT bidder bids again freely, then it shows a strong two suiter. To distinguish the weak and strong holdings, many partnerships agree not to use the unusual notrump for intermediate hands (about 12 to 14 points); they would simply overcall with one of their suits and show the other later if the bidding offers a chance. However, for two-suiters, many players apply losing trick count (LTC) instead of point count, as it more accurately depicts the offensive trick-taking potential of the hand. With LTC in effect, the required strength is about 4.5–7 losers, the latter only in favorable vulnerability.

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