An announcement is a way to inform the opponents the meaning of some calls which is usually treated differently by different people (e.g. the range of 1NT opening).
An announcement is made by the partner to the one making announceable call, by saying the word/phrase required by regulation.
ACBL[]
The following has to be announced:
- short minor openings, by saying "could be X", where X is the minimum length;
- The range of 1NT opening;
- Any artificial bid which shows length in a specific suit, or artificial double / redouble showing the next higher suit, by saying the suit. This doesn't apply to suits in which you or your partner has already shown length.
- Forcing or semi-forcing 1NT response, by saying the word "forcing" or "semi-forcing", and saying "could have spades" if the sequence 1♥ - 1NT does not deny 4 spades.
EBU[]
The following has to be announced:
- If a 1♣ or 1♦ opening may contain 2 cards or less;
- The range of a natural 1NT or 2NT opening;
- When a 1NT opening "may contain a singleton";
- Precision 2♣, by saying "intermediate";
- weak two openings, by saying "weak";
- strong two openings, by saying "strong, non-forcing" or "strong, forcing";
- Stayman;
- Jacoby transfer to majors, by saying "hearts" or "spades".