1M:2C = clubs or balanced, GF unless clubs are rebid.

In what follows, "M" denotes the major suit opened, and "OM" is the other major.


1. Responses to 2C
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Opener's hands are initially divided into two ranges of strength, which we refer to as MIN and MAX. The shape of the hand is divided into four main categories:

(i) single-suited hands: 6+ cards in M, no other 4-card suit
(ii) balanced hands (5-3-3-2 shape)
(iii) 5+/4 two-suiters
(iv) 5+/5+ two-suiters

Hands with 5-4-4-0 or 7-4-1-1 shape are dealt with separately.

The responses to 2C are as follows:

2D = any MIN with at most 3 cards in OM.
2H = 4+ OM, any strength. (But not a MAX 5-4-4-0.)
2S = MAX, balanced or 4+ diamonds
2N = MAX, 6+ M, no other 4-card suit
3C = MAX, precisely 4 clubs
3D = MAX, 5+ clubs
3H = MAX, 5-4-4-0 void in OM
3S = MAX, 5-4-4-0 void in diamonds
3N = MAX, 5-4-4-0 void in clubs
4C = MAX, 7-4-1-1 with 4 clubs
4D = MAX, 7-4-1-1 with 4 diamonds



2. Further relays to complete the basic description of the hand
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After 1M:2C,2D responder's 2H is a relay, with responses symmetric to the ones for MAX hands above. So

2S = MIN, balanced or 4+ diamonds
2N = MIN, 6+ M, no other 4-card suit
3C = MIN, precisely 4 clubs
3D = MIN, 5+ clubs
3H = MIN, 5-4-4-0 void in OM
4C = MIN, 7-4-1-1 with 4 clubs
4D = MIN, 7-4-1-1 with 4 diamonds


After 1M:2C,2H the relay is 2S:

2N = any MAX except 7-4-1-1 (and now 3C is a relay, with 3D showing 5+ cards in OM, 3H+ showing precisely 4)
3C = MIN, precisely 4 cards in OM
3D = MIN, 5+ cards in OM
3H = MIN, 5-4-4-0 void in diamonds
3S = MIN, 5-4-4-0 void in clubs
3N = MIN, 7-4-1-1
4C = MAX, 7-4-1-1


After 1M:2C,2S or 1M:2C,2D:2H,2S, 2N is a relay with responses

3C = balanced
3D = 5+ diamonds
3H+ = precisely 4 diamonds


3. Symmetric relay after the basic description of the hand is complete
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single-suiters are shown by a bid of 2N
balanced hands are shown by a bid of 3C
5+/4 two-suiters are shown by a bid of 3C, or 3H+
5+/5+ two-suiters are shown by a bid of 3D

Further relays apply after this, e.g. for 5+/4 two-suiters

3H = high shortage
3S = 5-4-2-2
3N = low shortage 5-4-3-1
4C = low shortage 6-4-2-1
4D = low shortage 6-4-3-0
4H = low shortage 7-4-2-0


4. Relay breaks
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We "always" relay with balanced hands, and nearly always on hands with support for opener's major. So most relay breaks show unbalanced hands with clubs, short in opener's major. These breaks are usually natural, but when 3C is needed for some other purpose we use an artificial bid to show a game force with long clubs. Also, due to lack of space we have to use 1M:2C,2N:3M to show diamonds (the natural meaning is not so useful because we can relay with support).

1M:2C,2D:
2H = GF relay - balanced/semi-balanced OR support for partner's major OR 4 cards in OM
2S = GF, 6+ good clubs
2N = GF, three-suiter short in partner's major
3C = invitational with long clubs
3D = GF 5+ clubs and 4+ diamonds (usually weak in OM, else we would bid 2N insted)
3M = GF, support for opener's major and an excellent club suit
3OM = GF 6+ clubs and 5+ OM

1M:2C,2D:2H,2S/2N:
step = relay - balanced/semi-balanced OR support for opener's major
others = 5+ clubs and 4 cards in OM, natural(ish)

1M:2C,2H:
2S = GF relay - balanced/semi-balanced OR support for one of the majors
2N = GF, 5+ clubs and 4+ diamonds
3C = invitational with long clubs
3D = GF, 6+ good clubs
3M = GF, support for opener's major and an excellent club suit
3OM = GF, 6+ clubs and precisely 3 cards in OM

1M:2C,2S:
2N = relay
3C = 6+ good clubs
3D = 5+ clubs and 4+ diamonds
3M = support for opener's major and an excellent club suit
3OM = 5+ clubs and 4+ cards in OM

1M:2C,2N:
3C = relay
3D = 6+ good clubs
3M = 5+ clubs and 4+ diamonds, short in partner's major, unsuitable for 3N
3OM = 5+ clubs and 4+ cards in OM, short in partner's major, unsuitable for 3N
3N = short in partner's major, other suits stopped

When opener has shown clubs, or when responder has promised either a balanced hand or support by relaying once, breaks below 3N are stopper-showing looking for 3N. These bids do not promise clubs (in fact responder is often known to be balanced at this point). For example,

1M:2C,3C:
3D = relay
3M = stop in diamonds: worried about the other major
3OM = stop in suit bid: worried about diamonds