Question

What is called young modulas of a material?

Answer 1

young's modulus of elasticity is defined as it is the ratio of normal stress to the strain in the longitudinal direction.
you can understand like how much force per unit area you apply on the body and due to that force or stress(force per unit area) how much body get deformed in the longitudinal direction and the ratio of that stress to deformation is known as Young's modulus of elasticity. its unit is N/m^2 and it is constant for a material.