[Adam1105]

Opener bids 1NT. Opoener's LHO bids 2D. Does "double" by responder equal staymen or transfer to hearts? Thank you.

[ahydra]

You have to agree what it means - for example, it could be for takeout, or (normally in a Lebensohl structure) for penalty. Playing it as stayman or as a transfer would be rather unusual, but that's fine if you and your partner agree on this particular meaning.

Someone else should comment on what the default "expert" meaning is - the EBU simple system defines it as takeout, but a good number of people play it as penalty here in England, and goodness knows what the situation is elsewhere.

ahydra

[helene_t]

1NT-(2♦)-x

Assuming that 2♦ is natural, the traditional way of playing it is penalty (opener always passes). The modern trend is to play it as takeout (opener needs four diamonds to pass), and that is what you should probably assume if undiscussed. This is on the top ten list of important things to discuss in a new partnership. There are also some that play it as "optional", i.e. opener will often pass with three diamonds but not with two.

In some circles it has become popular to play it as a transfer to hearts. This is not recomended by textbooks because it is too difficult for opener to decide whether to pass it or not, even with four diamonds and two hearts it may be bad as responder could have a weak hand with six hearts.

Personally I don't think it is very bad to play it as transfer, after all it is extra important to make opener declare when opener's LHO makes a lead directing overcall so that a diamond lead will go through the strong dummy if opener becomes dummy. But somehow transfer doubles ("stolen bid") has become associated with weak players so it may stigmatise you if you play it.

If 2♦ is Capp, the most popular meaning of dbl is that it shows interest in penaltizing their major suit contract, but that has the disadvantage that it gives opps the opportunity to use rdbl to ask for overcaller's longer major. In any case you should not double if you know that you want to double them for penalty - only if you want opener to cooperate in the decision making.

Alternatively you could play double as showing diamonds.

If 2♦ is multi-landy the situation is similar to Capp except that now you could play it as a transfer if you want since opps don't necesarily have hearts.

If 2♦ is DONT just pretend that it is a natural bid, i.e. double would be penalty or t/o or optional depending on what it would be against a natural 2♦ bid.