- You hold 13 tiles in play, and 14 only at the moment you declare Mah Jongg. Any other count — one over, one short — is dead.
- A joker fills a gap in a group of three or more. It is never a pair and never a single tile.
- Only another player may call your hand dead. You cannot declare it yourself, and you cannot quietly fix it.
- Everything else is judged from what is visible — discards and exposures — never from guesses about someone's rack.
Two worked cases
Case 1 · One tile too many
It is the middle of the hand. You have just taken your discard back off the table and picked it up again by mistake.
Your rack
- Count the rack: fifteen tiles are sitting there.
- The rule allows fourteen in one situation only — the instant you declare Mah Jongg. Any other time it is thirteen.
- Fifteen is not thirteen, so the hand is dead. Nothing you do next repairs it.
Dead — and you may not call it yourself. Keep discarding defensively and wait for someone else to notice.
Case 2 · A joker doing a pair's job
You hold one 5-dot and a joker, and you expose them together as a pair.
The exposure
- Two tiles are exposed: a 5-dot and a joker, called as a pair.
- Jokers complete groups of three or more. A pair is two — the one thing a joker may never be.
- So the exposure itself is illegal, and the hand is dead the moment it goes on the rack.
Dead — same joker in a pung of 5s would have been perfectly legal.
Eight drills
Each one shows a rack, an exposure or both. Call it dead or alive — the reason appears either way.
No card lines or point values appear here on purpose: the official card is the authority on what wins. This drills the mechanics that end a hand.