Lebensohl over Reverses

Some of the most difficult and awkward of all bridge auctions are those after a reverse. A reverse (see the lesson on this site) is opener's 2-level rebid in a higher-ranking suit than his opened suit (1C-1S-2D or 2H). A reverse always shows extra values and at least 5-4 distribution in the two suits.
A reverse is forcing for one round, but it may be made with as few as 16-17 pts., so it does not promise forcing-to-game values. Stopping below game, though, can sometimes be a problem. Because the reverse uses up so much bidding space, it can often propel the auction into an unmakeable game when both responder and opener have minimums.
To solve this problem, many partnerships have adopted a convention called Lebensohl over Reverses. After opener's reverse, responder uses a 2NT rebid to show a weak hand (5-7 pts.) that wants to stop in a 3-level partscore if opener has minimum reverse values. Here's how it works:
Responder's use of 2NT Lebensohl

Lebehsohl 2NT is used at your second bid after opener makes a reverse to the 2-level (1C-1S-2H). In this situation, 2NT by you usually shows weakness (5-7 pts.) and is a relay bid, asking partner to rebid 3C if he has a minimum (16-18 pts.).
After the auction:   Partner        You
                     1D              1S
                     2H             2NT (Lebensohl)
                     3C               ?
you have two ways to show weakness:

Pass = In this auction, clubs is the unbid suit, so you would pass the relay to 3C only if you had a 6+-card suit and no support for either of partner's suits -- Q954  Q3  7  QJ10842.
If partner's first suit was clubs, though, a pass here would show a weak hand with a preference for clubs (usually 3-card support) -- KJ542  83  QJ4  732 .

3 of one of partner's suits (3D or 3H) = a preference to play in a partscore in that suit.
A retreat to 3D would be made with a hand like  J1064  K3  J76  Q843.
You would bid 3H with  QJ743  8643  65  K4 or even  K954  Q103  4  J9543.

Although the Lebensohl 2NT is usually used with a weak response, you can also use it to start the description of a stronger hand that has a 6-card suit. In the above auction, after partner bids 3C, you can bid 3S to show a forcing-to-game hand (8+ pts.) with 6 spades -- a hand like  K108742  J3  104  AJ8 .
Note that if opener refuses your relay and bids past 3C, he's showing significant extra strength. You must keep bidding to game level, no matter how weak you are.
Opener's rebid after 2NT

If responder bids 2NT over your reverse, it's the Lebensohl convention, which asks you to bid 3C. You should accept the relay and bid 3C if you have minimum values (16-18 pts.). However, with stronger hands -- those where you want to be in game, even if partner has a bare 5-7 pts. -- you can refuse the relay and bid past 3C.
After the auction:   You            Partner
                     1D              1S
                     2H             2NT (Lebensohl)
                      ?
here are the ways you can show a forcing-to-game hand (19+ playing pts.):

3D = Extra length in diamonds (6-card suit), probably with extreme shortness in clubs. You can use this bid to show a hand that has extra playing strength, but not necessarily a powerful high-card-point holding
-- J4  AK107  AKJ10974  Void.
    If you had instead opened 1C, though, 3D would be the fourth suit here. Some pairs use this bid as natural
-- if you opened 1C, a hand like  Void  KQJ3  AJ104  AKJ92 . Others use it as a general force to show a strong hand with no other "obvious" rebid, usually because of the lack of a stopper in the unbid suit
-- J4  AKQ3 84 AKQ102 .

3 of your second suit (3H) = Extra length in your second suit. A reverse promises greater length in your first suit, so a rebid of your second suit here shows 5 hearts and 6 diamonds -- 4  KQ1032  AKQ764  A .

3 of partner's suit (3S) = 3-card support. It's advisable to stretch somewhat if you have secondary support for partner's major, so you may refuse the relay here with a good 17-18 pts. -- QJ8  AK93  AK1084  3 .

3NT = Strong hand with at least one good stopper in the unbid suit -- Q  AJ103  KQJ103  AQ4 .

Other actions by responder after a reverse

Having the Lebensohl 2NT available will change the meanings of some of your other rebids. After the reverse, if responder makes any bid past 2NT, it shows forcing-to-game values.
After the auction:   You            Partner
                     1D              1S
                     2H               ?
here are the meanings of your other actions:

Preference to partner's first suit (3D) = 3+-card support and forcing-to-game values (8+ pts.)
-- A984  1093  J104  A82.

Jump in partner's first suit (4D) = 4-5+-card support and slam values (12+ playing pts.)
-- A984  3  Q10754  AJ4.

Raise of partner's second suit (3H) = 4-card support and forcing-to-game values (8+ pts.)
-- KJ874  K1053  Q4  54.

Rebid of your own suit (2S) = at least 5 (preferably 6) cards in your suit and a weak hand (5-7 pts.)
-- QJ9762  93  74  K54. Opener can pass this if he has a minimum, non-fitting reverse (16-17 pts.).

Jump in your own suit (3S) = strong 6+-card suit (at least 3-4 of the top 5 honors) and good values (8+ pts.)
-- KQJ1075  93  J4  A102.
If you have a weaker 6-card suit, use the Lebensohl 2NT first, then bid 3S over partner's 3C bid.

Jump to game in your suit (4S) = solid 6-7+-card suit that should play for no losers opposite a singleton
-- AKQ9854  J103  4  82.

The unbid suit (3C) = forcing and could be artificial. Like "New Minor Forcing", this bid can be used when you have good values (8+ pts.) and 5 cards in your first suit -- -- KQ974  843  A4  982 .
Opener will bid 3 of your suit if he has 3-card support, or will make another descriptive bid if he doesn't.

Jump in the unbid suit (4C) = splinter, showing a singleton in that suit, 4-card support for partner's second suit, and at least slam-try values -- AK842   Q1073  Q74  4 .

　