What is Stress and Strain?

[Nickjohny]

It has the dimension of force per area or the same dimension as that of pressure. It is called stress.

It is a fraction which compares the change in the configuration of the body to the original configuration of the body. It is called Strain.
 

[Lorentz Jr]

Stress is the external influence being exerted on the system.

Strain is the system's passive response to the stress, giving in or succumbing to it.

[studiot]

1 hour ago, Nickjohny said:

It has the dimension of force per area or the same dimension as that of pressure. It is called stress.

It is a fraction which compares the change in the configuration of the body to the original configuration of the body. It is called Strain.
 

Yes, stress can be thought of very simply as force per unit area, but there is much more to it than this because that force can be applied in one of two mutually perpendicular directions viz perpendicular to the area under consideration or parallel to it.
If the force is applied at some other angle then it can be resolved into components parallel and perpendicular to the area.
Stress is an internal force to some body. External forces are useually called loads.

All real world bodies respond to stress by exhibiting strain, although it is often very small so we often work in units of microstrain.

When the strain is to small to worry about, we call the body a rigid body.

Strain is sometimes the result of that stress, but no always. Bodies also exhibit strain when their temperature increases and if they are free to expnad we observe stress free strain.

Finally strain can also be resolved into components, like stress.

 

Does this help ?