Mochikomi

Mochikomi is a stone or group of stones lost to the opponent as a gift. This may happen because of a bad move, or through an intentional sacrifice that receives no adequate compensation. The opponent is allowed to capture the offered stones, so they become lost stones or prisoners for the player who made the offer.

The term describes the material cost of a play, especially when stones are surrendered without sufficient return. It differs from suteishi, which specifically means an intentional sacrificial stone: mochikomi emphasizes stones that have been lost or handed over, often through a mistake. A sacrifice is not necessarily mochikomi if it produces adequate compensation; mochikomi generally implies an unfavorable or gratuitous loss.