The difference between tensional, extensional, and compression forces.

The difference between compression and tension is that a compressing force causes an object to shorten in the direction of the force, while a tension force causes an object to lengthen in the direction of the force. Regardless of the strength of the material, compression and tension forces always cause some amount of deformation. 

 Side B'A' has a slope of 1 and is parallel to side BA.