| Concentrated force: | (english) A force considered to act along a single line in space. Concentrated forces are useful mathematical idealizations, but cannot be found in the real world, where all forces are either body forces acting over a volume or surface forces acting over an area. |
| Connection: | (english) Connection is similar to the concept of support, except that connection refers to a relationship between members in a structural model. A connection restrains degrees of freedom of one member with respect to another. For each restrained degree of freedom, there is a corresponding force transferred from one member to the other; forces associated with unrestrained degrees of freedom are zero. See fixed connection and pin connection. |
| Couple: | (english) A system of forces composed of two equal forces of opposite direction, offset by a distance. A couple is statically equivalent to a moment whose magnitude equals the magnitude of the force times the offset distance. |
| Deflection: | (english) This word usually carries the same meaning as displacement, although it is sometimes used in place of deformation. |
| Deformation: | (english) A change in the shape of an object or material. |
| Degree of Freedom: | (english) A displacement quantity which defines the shape and location of an object. In the two dimensional plane, a rigid object has three degrees of freedom: two translations and one rotation. In three dimensional space, a rigid object has six degrees of freedom (three translations and three rotations). |
| Displacement: | (english) A change in position. A displacement may be a translation a rotation or a combination of those. |
| Distributed load: | (english) An external force which acts over a region of length, surface, or area: essentially any external force which is not a concentrated force. |
| 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. |