rígido

Rígido is an adjective used in Portuguese and Spanish to denote stiffness or inflexibility. Etymologically, it derives from Latin rigidus and is cognate with the English word rigid. In both languages the term describes physical properties, as well as attitudes, rules, or policies that resist deformation or change.

In science and engineering, a rigid body is an idealization in which the distances between all points remain constant under external forces. A rigid motion is a transformation that preserves distances. Real materials exhibit varying degrees of rigidity and are characterized by stiffness, often quantified by properties such as the modulus of elasticity. The concept underpins mechanics, robotics, computer graphics, and structural design.

In everyday language, rígido conveys inflexibility in behavior, routines, or policies, such as a rigid schedule or a rigid organizational culture. In medicine, rigidity refers to stiffness of muscles or joints, and rigor mortis describes the postmortem stiffening of a body. The term can also describe formalism or doctrinal inflexibility in social or academic contexts.

The word is used similarly in Spanish and Portuguese, with regional variations in nuance and usage. Related terms include rigidity, stiff ness, and, in physics, rigid body and rigid motion, which form part of the technical vocabulary for describing nondeformable or nearly nondeformable systems.