What is mechanical stress?

I would Ike to be more explanatory on this.

when force is applied on object(e.g. a piece )certain area or ideally speaking whole area (c/s) tries to elongate or compress.but due to elastic property of material,piece on which force is acted,tries to regain its past shape or stage so one resistant force is developed.This force is called stress.and stress intensity is given by:

mechanical stress is force divided by area

σ=F/A

if unit of F is Newton and area in Sq. m

then mech. stress is in Pascal