jäikuse

Jäikuse is an Estonian noun that translates as rigidity or stiffness. The term is used across disciplines to denote a state of being stiff, inflexible, or resistant to change, and it can describe physical properties, biological conditions, or social attitudes.

In physics and engineering, jäikuse refers to the resistance of a material or structure to deformation under applied loads. It is often quantified by elastic moduli, such as Young's modulus and the shear modulus; higher values indicate greater rigidity. In theoretical terms, a perfectly rigid body would experience no deformation regardless of the force applied, though such bodies do not exist in practice.

In medicine and neurology, jäikuse describes muscle rigidity, a form of increased muscle tone. This can be a characteristic of extrapyramidal disorders such as Parkinson's disease, where muscles show uniform resistance to passive movement. Rigidity is distinct from spasticity—in part because it is less dependent on movement velocity—and from flaccidity, which denotes limpness. Clinical assessment may involve observing tone across different joints and during varied movements.

In everyday language, jäikuse is used to describe inflexibility in opinions, routines, or social behavior. It can refer to a reluctance to adopt new ideas or to a stiff, formal, or unforgiving attitude in interpersonal interactions.

See also: rigidity, stiffness.