How is the flexibility of a structure defined?

The flexibility of a structure is defined as the inverse of stiffness. This relationship is rooted in the fundamental principles of structural engineering, where stiffness refers to a structure's ability to resist deformation under load. When stiffness increases, flexibility decreases, and vice versa.

Flexibility quantifies how much a structure will deform (deflect) under a given load. It indicates the ease with which a structure can change shape when subjected to loads, effectively illustrating how responsive or compliant the structure is. Mathematically, flexibility can be expressed as the deflection per unit load, and its reciprocal gives the stiffness. Thus, understanding this relationship helps engineers design structures that can withstand various forces without failing.

In contrast, the other options do not accurately reflect the definition of flexibility. For instance, the ratio of load to deflection might imply a relationship with rigidity rather than flexibility, while proportionality to height and mass primarily relates to design considerations rather than the inherent flexibility of the material or structure itself.