What furiten means
Furiten is the rule that stops you from claiming a ron on a winning tile you have already discarded yourself. If any of the tiles that complete your hand sits in your kawa, you are in furiten on your entire wait, not only on that one tile.
Temporary furiten in Tenhou and WRC
While in furiten the hand stays valid but can only win by tsumo. Temporary furiten happens when you pass a tile that completes a valid winning shape, even if that shape has no yaku. Under Tenhou rules, it clears after your next discard, and a call that reverses turn order does not clear it immediately. WRC 2025 clears it on your next draw or your own call.
Furiten after riichi
After riichi, furiten becomes permanent for the rest of the hand the moment you let a tile that completes the hand pass. Checking your wait before you discard and before you declare riichi is an essential habit.