Most good players play that when opening bidder "reverses," it shows 17 HCP and is forcing for one round. A reverse occurs when the opening bidder bids an unbid higher ranking suit at the two level than she bid at the one level, like opening 1 club and then bidding 2 hearts at her second bidding opportunity. If she opens 1 heart and then bids 2 clubs at the two level at her second bidding opportunity, it is not a reverse. But what does a reverse by responder show? Here's a hand that occurred recently:
Dealer East. Nobody vulnerable.
♠ J96 ♠ 854
♥ Q7 ♥ A83
♦ AKT842 ♦ 96
♣ 32 ♣ JT764
West North East South
1D 1H P 2C
P 2N P 3N
P P P
Opening Lead: 9D
Bidding: South has a decision. Should this be opened 1C or 3C? She only has 11 HCP, but she's got a terrific six card suit. If all she had were 6 clubs headed by the AKQ, she could open this 3C, but there are two things that argue against this. The first is that the queen of spades gives her 11 HCP, which is too many points to preempt, especially when you are in second seat and are preempting your partner. Second, she has not one, but two three card majors. Many players don't like to preempt in a minor when they hold a three card major because it makes it hard, certainly improbable, to find a 5-3 fit in that major if partner has five of them. Here, since she has three cards in both majors, it argues against a preempt, so she opened 1C.
North properly bids her 5 card heart suit. South rebids her clubs. This yells at partner, "I have a weak hand whose only feature is clubs." Here's where North misbid. First, she must understand that a negative double by her (instead of bidding 1 heart) would promise two four-card majors. Over 1C-1D overcall, a 1 heart response could show only four hearts because she could have, for instance, four hearts and two spades. In this instance, she cannot make a negative double, so when she bids 1 heart, South doesn't yet know whether she has four hearts or five or more hearts. So she has to make another bid to show that she has five hearts.
Not understanding the rules about reverses, she bids 2N. How wrong is this? Let me count the ways. First, it tells South that she has 3 clubs, implies that she has all the unbid suits stopped, and is asking if south's club suit is really good to go to 3N because they should have six club tricks. Second, she's void in partner's strong suit. That's a huge weakness in no trump. For one thing she might not ever be able to get to dummy's long suit. Secondly, almost certainly she won't get six, or even five, tricks in the long suit. Third, when responder bids 2N in her second response to an opening bid of one of a suit shows 11-12 HCP, so this is a big underbid since she actually has 14 HCP. Fourth, she didn't show her five card suit. Her bid only promises four hearts, so how is her partner to know she actually has a five card heart suit?
What makes this bidding so bad is that she had two tailor-made bids. The first is 2D, which is called "new minor forcing," and shows five cards in the major suit she bid, hearts and a minimum of 9-10 HCP. It says nothing about the diamond suit.
The second bid she has is to reverse into 2 spades, since she has four of them. This is the preferable bid because it shows her strength. New minor forcing only shows a minimum of 10 HCP. A reverse by responder shows a full opening hand. The rules for responder to reverse are lighter than for opener. If responder reverses, it only shows an opening hand. Here, responder has a good 14 HCP and four spades. She should reverse and bid 2S, which shows partner a game-going hand and five hearts.
No matter which route she takes, New Minor Forcing or a reverse, both show 5 hearts, allowing south to support her by bidding 3H, thereby showing 3 hearts in her hand, and North can go to game in hearts, which makes. 3N can make, too, but it has to be carefully played. Still, with two distributional hands (North has a void and south has a singleton), this hand should be played in a suit, hearts.
Here's how the bidding should have gone:
West North East South
1D 1H P 2C
P 2S P 3H
P 4H P P