Young's modulus is a measure of a material's elasticity, defined as the ratio of stress to strain in the linear elastic region of deformation. It quantifies how much a material will deform under applied pressure, indicating its resistance to stretching. The formula for Young's modulus is E = σ/ε, where σ is the applied stress and ε is the strain. This concept is primarily applicable to Hookean materials undergoing uniaxial deformation, such as rods. Understanding Young's modulus is essential for predicting material behavior in engineering and construction applications.