The coefficient of elasticity of stretching. Within the limits of elasticity, the ratio of the linear stress to the linear strain is termed the modulus of elasticity or Young's Modulus and may be written Young's Modulus, Modulus of Elasticity or E =(Stress/Strain). It is this property that determines how much a bar will sag under its own weight or under a loading when used as a beam within its limit of proportionality. For steel, Young's Modulus is of the order of 200,000 N/mm^2 or 200 MPa.