Ippatsu

Also called: 一発, one-shot

Riichi-only: extra 1 han for winning within one uninterrupted turn after declaring riichi.

Ippatsu is a Riichi-only bonus worth 1 han. After declaring riichi, if you win within one full turn cycle (no opponent has called a meld, no one has declared kong, and no one has called pon/chi/kan), you get the ippatsu bonus. It's broken by any interrupting call. Some online rules disable ippatsu — check before declaring riichi if it matters.

Related terms

Riichi
Japanese-only declaration: bet 1,000 points on a closed tenpai for guaranteed yaku.
Yaku
Japanese-only term for a named scoring pattern. Every winning Riichi hand needs at least one yaku.