JACOBY 2NT ("Original")
(Click here for more advanced "modified" version)
Most tournament players use "JACOBY 2NT" in conjunction with their 5-card major system. After an opening of 1-MAJ, a jump to 2NT is conventional. It promises a GF hand and at least 4-card support.
This convention should not be used by a passed hand and should not be used if there is interference by the opponents. I can't warn you enough how important it is when employing any convention to cover this vital issue (on by PH?--on in comp?).
In the "original" (most popular, stilll) version of this convention, this is the schedule of rebids for the opener after the Jacoby 2NT response:
4 of the trump suit=minimum, no shortness
3 of the trump suit=non-minimum, no shortness
3 of a new suit = shortness (singleton or void)
3NT=varying ways to play this, sometimes a sixth card in your major
4 of a new suit = good side 5-card suit (some people instead use this to show a void)
At any point, by either player, bidding 4-of-the-major which was opened is always the weakest (sign-off) action.
Other bids after the Jacoby 2NT and opener's rebid are control-bids-- this can be a singleton (or void), ace or king.
My suggestion is that you learn those 3-level bids, and don't worry much about the 4-level bids as those tend to make auctions more difficult. It can be very helpful to know where a singleton is when you have a 9-card fit. For example, look at these two hands:
North opens 1 and South uses Jacoby 2NT with a 14-count. North's heart singleton is tremendously helpful for South. Look at how all of South's cards are working. Now, South can envision this excellent slam with only 26HCP combined.
As stated above, this convention is never on if they interfere after our 1MAJ opening. However, we do need to cope if they interfere after the 2NT response:
Opener's double = Shortness in suit doubled
Opener's new suits = natural or a control
3NT = Balanced Maximum (Ace or King in their suit)
Opener's Pass = Nothing special--flat hand, could be 5-3-3-2 awful after which, responder's X=penalty
Opener's jump to 4M = dead minimum, but 6-3-2-2
Mike Lawrence Webinar on Jacoby 2NT
Updated: Jan 2023