Stiffness:This is a general term which may be applied tomaterials or structures. When a force is applied to a structure, thereis a displacement in the direction of the force; stiffness is the ratioof the force divided by the displacement. High stiffness means that alarge force produces a small displacement. When discussing thestiffness of a material, the concept is the same, except that stresssubstitutes for force, and strain substitutes for displacement; seemodulus of elasticity.