The measure of how much an object resists deformation is known as its stiffness, which indicates the object's ability to maintain its shape under applied forces. This property is crucial in materials science and engineering when selecting substances for specific applications. Stiffness can be quantified using the elastic modulus, which relates stress to strain within the elastic limit of a material. Understanding stiffness helps engineers design structures and components that can withstand loads while minimizing deflection and failure.