| Ductility: | (english) Ductility generally refers to the amount of inelastic deformation which a material or structure experiences before complete failure. Quantitatively, ductility can be defined as the ratio of the total displacement or strain at failure, divided by the displacement or strain at the elastic limit. |
| Dynamic equilibrium: | (english) Equilibrium which includes inertial forces. |
| Elastic: | (english) A material or structure is said to behave elastically if it returns to its original geometry upon unloading. |
| Elastic energy: | (english) The energy stored in deformed elastic material (e.g., a watch spring). Elastic energy equals where k is the stiffness, and is the associated deflection. Elastic energy is sometimes called elastic potential energy because it can be recovered when the object returns to its original shape; see potential energy. |
| Elastic limit: | (english) The point beyond which the deformations of a structure or material are no longer purely elastic. |
| Energy: | (english) A property of a body related to its ability to move a force through a distance opposite the force's direction; energy is the product of the magnitude of the force times the distance. Energy may take several forms: see kinetic energy, potential energy, and elastic energy. |
| Equilibrium: | (english) An object is in equilibrium if the resultant of the system of forces acting on it has zero magnitude. See static equilibrium and dynamic equilibrium. |
| External force: | (english) A surface force or body force acting on an object. External forces are sometimes called applied forces. |
| Fixed connection: | (english) In two dimensions, a fixed connection between two members restrains all three degrees of freedom of the connected member with respect to one another. A fixed connection is sometimes called a rigid connection or moment-resisting connection. |
| Flexibility: | (english) Flexibility is the inverse of stiffness. When a force is applied to a structure, there is a displacement in the direction of the force; flexibility is the ratio of the displacement divided by the force. High flexibility means that a small load produces a large displacement. |