Vampyr, on 2013-January-09, 22:55, said:
A negative double is generally a takeout double, although sometimes it has certain additional features, such as promising or denying a four-card spade suit. But all takeout doubles are not negative doubles; far from it.
I have no idea what you are assuming the word "negative" means in this context; I believe that the word came to be used because your hand has a "negative" feature precluding the bidding of a new suit at the necessary level. For example, not enough cards in the suit or not enough HCP.
With all due respect, Vampyr, the definition of a "negative" double is a double that is not a penalty (i.e., positive) double. It is, by definition, a takeout double.
Admittedly, depending on the situation, there are specific requirements on negative doubles, and various partnerships play them differently in different situations. The classic takeout double occurs when the opponents open the bidding and the player in direct seat after the opening bidder doubles. A balancing double is a takeout double. Doubles of opening preempts at the 2 and 3 levels are played as takeout doubles by a vast majority of players.
According to Wikipedia, this is a brief history of the use of the term "negative double:"
The term negative double was initially employed to distinguish it from the penalty, or business, or positive double, and signified a double over an opponent's opening bid whose meaning was a request for partner to bid his best suit. Around 1930, the term informatory double replaced negative double, and that term later gave way to takeout double as it is used at present; the original term negative double fell into disuse.
In 1957, Alvin Roth in his partnership with Tobias Stone appropriated the abandoned term negative double to denote a conventional double by responder over an overcall and gave it its current meaning. The bid was also briefly known as Sputnik, because it was as new as the satellite of that name that the Soviet Union had recently launched. The term is still used sometimes in Europe.
So, in current popular usage, the term "negative double" is reserved for the double made by the partner of the opening bidder after intervention. But the fact is that negative doubles are any doubles that are not positive (i.e. penalty) doubles.
What is really being discussed in the OP and in this thread in general is what most players would refer to as an optional double. Rather than being strictly a takeout double, the optional double is a card showing double. Partner should pass an optional double for penalties far more often than he should pass a takeout double for penalties. And, conversely, partner should be more wary of bidding over an optional double as the doubler's hand may not contain good support for each of the unbid suits. The double of 5
♣ should be an optional double due to the level of the auction. One must be able to show a good hand over a high level preempt without the restrictions that typically apply to a takeout double.