[cnszsun]

1C-(1S)-DBL-(Pass)
2D
Some say double only promises hearts and opener's 2d is similar to reverse. What's the commom understanding?

[Zelandakh]

If you play X in the traditional way, as takeout, then 2♦ does not show extras. If you play X in the more common way where it shows hearts but says nothing about diamonds, then the rebid shows extras. The "common understanding" is the latter.

[helene_t]

We have had this discussion many times and there is no consensus. One thing i think everybody agrees on is that opener shouldn't bid this way with only four clubs and a minum since he can't tolerate responder taking preference to clubs . But most of us open 1d with 4-4 minors anyway .
If you play that 2d is 12-15 you have to
- discuss what to do with 16-17
- don't make negative doubles with weak hands with 2-2 in the minors

[gwnn]

http://www.bridgebas...egative-double/
http://www.bridgebas...egative-double/
http://www.bridgebas...-play-this-one/
http://www.bridgebas...a-good-partner/
http://www.bridgebas...-many-controls/
http://www.bridgebas...-not-a-reverse/

I'm sure I missed many others. It's one of the two most common questions here (the other one being what you open on 1345 - actually the two questions are related).

As it has been posted many times in the above threads and the ones I missed, according to the BW standard from 2001, it is not, however, a reverse.

BW Standard said:

Negative doubles: A negative double at the one level or when there is exactly one unbid major guarantees at least four cards in any unbid major (opener may rebid in a three-card suit there in a pinch); otherwise, that requirement is only tentative (opener should not rebid in a three-card suit). When responder’s negative double guarantees length in an unbid major, opener’s bids in that suit function as would raises in the corresponding noncompetitive auction. After one club — (one of a major) — double — (pass) — ?, opener’s two-diamond rebid does not show extra values.

[wangzhi123]

a reverse！if opener hold 44 minor ，he open id！if 54 bid 2c