Empty triangle
A compact three-stone formation that usually represents inefficient shape.
An empty triangle is a formation of three connected stones occupying three points of a compact triangular pattern, while the fourth point remains vacant. The stones are connected around that empty point, typically forming three corners of a 2×2-square arrangement. This usually spends an extra stone without substantially improving liberties, influence, or eye space.
Recognizing an empty triangle helps players avoid inefficient shape and spot unnecessary overconcentration or loss of flexibility. Unlike an efficient shape such as a tiger shape, it is normally considered bad shape: the empty point contributes little, while the three stones can remain vulnerable to tactical pressure. It is not automatically a mistake, however. The formation may be correct when connection, life, attack, defense, or a specific tactical sequence requires it.
This term in other languages