Rigid or rigidity may refer to:

Mathematics and physics

Stiffness Stiffness is the extent to which an object resists deformation in response to an applied force. The complementary concept is flexibility or pliability: the more flexible an object is, the less stiff it is. Calculations The stiffness, k, of a ...

, the property of a solid body to resist deformation, which is sometimes referred to as rigidity *

Structural rigidity In discrete geometry and mechanics, structural rigidity is a combinatorial theory for predicting the flexibility of ensembles formed by rigid bodies connected by flexible linkages or hinges. Definitions Rigidity is the property of a structu ...

, 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) In mathematics, a rigid collection ''C'' of mathematical objects (for instance sets or functions) is one in which every ''c'' ∈ ''C'' is uniquely determined by less information about ''c'' than one would expect. The above statement doe ...

, a property of a collection of mathematical objects (for instance sets or functions) *

Rigid body In physics, a rigid body, also known as a rigid object, is a solid body in which deformation is zero or negligible, when a deforming pressure or deforming force is applied on it. The distance between any two given points on a rigid body rema ...

, in physics, a simplification of the concept of an object to allow for modelling *

Rigid transformation In mathematics, a rigid transformation (also called Euclidean transformation or Euclidean isometry) is a geometric transformation of a Euclidean space that preserves the Euclidean distance between every pair of points. The 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) Spasticity () is a feature of altered skeletal muscle performance with a combination of paralysis, increased tendon reflex activity, and hypertonia. It is also colloquially referred to as an unusual "tightness", stiffness, or "pull" of muscle ...

, 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 In economics, nominal rigidity, also known as price-stickiness or wage-stickiness, is a situation in which a nominal price is resistant to change. Complete nominal rigidity occurs when a price is fixed in nominal terms for a relevant period of tim ...

, the resistance of prices and wages to market changes in macroeconomics * Ridgid, a brand of tools {{disambiguation