Rigidity

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