Let's begin by clarifying the basic terms:
Strength: Strength of a material
refers to its ability to withstand an applied load without failure or deformation. Stiffness:
On the other hand, stiffness of material, or in more formal terms, the modulus of elasticity, measures a material's resistance to elastic deformation under load.
To put it simply, the stronger the material, the more load it can handle without breaking. The stiffer the material, the less it will deform under a given load.