Updated: Aug 16, 2020
Stress and Strain are fundamentals of the Civil Engineering discipline and are not to be confused
Solid Mechanics look into various material's motion and deformation under the action of forces.
Stress is the ratio of applied force F to a cross-section area - defined as "force per unit area".
The idea of stress could be used to describe the state of affairs at any point inside a solid in a much more general way. Also, stress could be used to predict when the material will break.
"Stress tells us how hard- that is, with how much force - the atoms at any point in a solid are being pulled apart"