| Pressure: | (english) Pressure is a similar idea to stress, the force intensity at a point, except that pressure means something acting on the surface of an object rather than within the material of the object. When discussing the pressure within a fluid, the meaning is equivalent to stress. |
| Reaction: | (english) A reaction is a force exerted by a support on an object: sometimes called support reaction. Using this definition, a reaction is an external force. |
| Resultant: | (english) The resultant of a system of forces is a single force or moment whose magnitude, direction, and location make it statically equivalent to the system of forces. |
| Shear: | (english) An system of internal forces whose resultant is a force acting perpendicular to the longitudinal axis of a structural member or assembly: sometimes called shear force. |
| Static equilibrium: | (english) Equilibrium which does not include inertial forces. |
| Statically determinate: | (english) A statically determinate structure is one where there is only one distribution of internal forces and reactions which satisfies equilibrium. In a statically determinate structure, internal forces and reactions can be determined by considering nothing more than equations of equilibrium. |
| Statically equivalent: | (english) Two force systems are statically equivalent when their resultants are equal. Physically, this means that the force systems tend to impart the same motion when applied to an object; note that the distribution of resulting internal forces in the object may be different. |
| Statically indeterminate: | (english) A statically indeterminate structure is one where there is more than one distribution of internal forces and/or reactions which satisfies equilibrium. |
| Stiffness: | (english) This is a general term which may be applied to materials or structures. When a force is applied to a structure, there is a displacement in the direction of the force; stiffness is the ratio of the force divided by the displacement. High stiffness means that a large force produces a small displacement. When discussing the stiffness of a material, the concept is the same, except that stress substitutes for force, and strain substitutes for displacement; see modulus of elasticity. |
| Stress resultant: | (english) A system of forces which is statically equivalent to a stress distribution over an area. |