Rigidity is the quality of being stiff, inflexible, or unwilling to bend or change. A metal rod has physical rigidity because you can't easily bend it with your hands. Ice has more rigidity than water because it holds its shape instead of flowing.

The word often describes attitudes or thinking, not just physical objects. Someone with mental rigidity sticks stubbornly to their ideas even when presented with good reasons to reconsider. If a teacher has rigid classroom rules that never adjust for special circumstances, students might feel frustrated. A coach with a rigid game plan might struggle when the other team does something unexpected.

Rigidity usually suggests a problem. While consistency matters, too much rigidity can mean missing opportunities or failing to adapt. A gymnast needs flexibility, not rigidity, to perform well. A friend who rigidly insists on always getting their way will struggle to maintain friendships.

Scientists and engineers sometimes value rigidity: a bridge needs structural rigidity to support weight safely. But even they know that some flexibility helps structures survive earthquakes and strong winds.