Rigid or rigidity may refer to: Mathematics and physics Stiffness, the property of a solid body to resist deformation, which is sometimes referred to as rigidity Structural rigidity, a mathematical theory of the stiffness of ensembles of rigid objects connected by hinges Rigidity (electromagnetism), the resistance of a charged particle to deflection by a magnetic field Rigidity (mathematics), a property of a collection of mathematical objects (for instance sets or functions) Rigid body, in physics, a simplification of the concept of an object to allow for modelling Rigid transformation, in mathematics, a rigid transformation preserves distances between every pair of points Rigidity (chemistry), the tendency of a substance to retain/maintain their shape when subjected to outside force (Modulus of) rigidity or shear modulus (material science), the tendency of a substance to retain/maintain their shape when subjected to outside force Medicine Rigidity (neurology), an increase in muscle tone leading to a resistance to passive movement throughout the range of motion Rigidity (psychology), an obstacle to problem solving which arises from over-dependence on prior experiences Other uses Real rigidity, and nominal rigidity, the resistance of prices and wages to market changes in macroeconomics Ridgid, a brand of tools