Young's modulus quantifies how much a material will deform under an applied force. It is defined as the ratio of stress (force per unit area) to strain (relative deformation) in a material. Mathematically, Young's modulus (E) is expressed as:

E = (Stress) / (Strain)

The unit of Young's modulus is usually in Pascals (Pa) or megapascals (MPa), depending on the unit system used.

A higher value of Young's modulus indicates that the material is more rigid and less deformable under stress, while a lower value suggests greater deformability.