(German, Elasticitats modulus, French, Module d'elasticite). The modulus of elasticity of a given material is the force required to elongate a piece of the material (whose area of cross-section is equal to one square inch) through space a distance equal to its primary length. Thus, if a bar of iron, twelve inches long, and of one square inch area of cross-section, could be made so elastic as to stretch to twice its length, the force required to stretch it until it were twenty-four inches long would be its modulus of elasticity in weight per square inch.