| Moment: | (english) The resultant of a system of forces causing rotation without translation. A moment can be expressed as a couple. |
| Moment of inertia (I): | (english) Moment of inertia has two distinct but related meanings: 1) it is a property of a an object relating to the magnitude of the moment required to rotate the object and overcome its inertia. 2) A property of a two dimensional cross section shape with respect to an axis, usually an axis through the centroid of the shape. |
| Normal strain: | (english) Strain measuring the intensity of deformation along an axis. Normal strain is usually denoted by . Average normal strain between two points is calculated as (Delta L / L), where L is the original distance between the points, and L is the change in that distance. Normal strain is often simply called strain. |
| Pin support: | (english) In two dimensions, a pin support restrains two translation degrees of freedom but does not restrain rotation. When considering reaction forces, a pin support is usually considered to have two force components: one each about the x and y axes respectively. |
| 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. |
| Rotation: | (english) Motion of an object where the path of every point is a circle or circular arc. A rotation is defined by a point and vector which determine the axis of rotation. The direction of the vector is the direction of the axis and the magnitude of the vector is the angle of rotation. |
| Section Modulus: | (english) A property of a cross sectional shape, which depends on shape, and orientation. Section modulus is usually denoted S, and S = I/c, where I = moment of inertia about an axis through the centroid, and c is the distance from the centroid to the extreme edge of the section. |
| 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. |
| 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. |