The definition of elastic modulus is the ratio of stress to strain in a material. Stress is defined as the force applied per unit area, and strain is defined as the deformation or change in length per unit length of a material under that stress. The elastic modulus is a measure of a material's stiffness and its resistance to deformation. The formula for elastic modulus is:
\(\frac{\text{stress}}{\text{strain}}\)
In simpler terms, elastic modulus is a number that tells us how much a material will stretch or compress under a given amount of force. A material with a high elastic modulus will be stiffer and less likely to deform, while a material with a low elastic modulus will be more flexible and more likely to deform.