What is the relationship between stiffness and modulus of elasticity in materials?

The relationship between stiffness and modulus of elasticity in materials is that they are directly proportional. This means that as the modulus of elasticity of a material increases, its stiffness also increases. Stiffness refers to how much a material resists deformation under an applied force, while modulus of elasticity measures the material's ability to return to its original shape after being deformed. Therefore, a higher modulus of elasticity indicates a stiffer material.