(i) Elasticity is the ability of a material to regain its original shape or size after deformations. OR after removal of stress force, OR after it has been 1 compressed. (ii) Young's Modulus is the ratio of tensile I or compressive stress to tensile or compressive strain (iii) Force constant = the amount of force that causes a unit extension of an elastic material. OR \(\frac{Force (F)}{ Extension(e)}\) of an elastic material.