Weakness

A weakness is a defect the opponent can use as a target or entry point. It may be a pawn that is hard to defend, a weak square, an exposed king, a vulnerable rank, meaning a weak horizontal row, or an inactive piece such as a bad bishop. The term is broader than any one example.

A defect becomes a practical weakness through its cost. A rook may have to defend a pawn instead of becoming active, several pieces may need to guard one square, or the king may be unable to leave an area. The attacker gains freedom to increase pressure, switch targets, or force further concessions.

Not every imperfection deserves an attack

An unusual pawn arrangement may provide open files, meaning vertical lines without pawns, or more room for pieces to maneuver. An apparently weak square may be inaccessible. Before building a plan around a defect, check whether you can reach it, maintain pressure, and improve your pieces without allowing more dangerous enemy threats.

A common method is to fix the weakness so it cannot advance or disappear, attack it with additional pieces, and force the opponent to defend. If one weakness is easy to protect, the attacker often creates a second target elsewhere. The defender tries to remove the target, exchange attacking pieces, or generate activity that compensates for the defensive burden.