Critical. A vulnerability whose exploitation could allow code execution without user interaction. These scenarios include self-propagating malware (e.g. network worms), or unavoidable common use scenarios where code execution occurs without warnings or prompts. This could mean browsing to a web page or opening email.
A strain is a stretching or tearing of muscle or tendon. A tendon is a fibrous cord of tissue that connects muscles to bones. Strains often occur in the lower back and in the hamstring muscle in the back of your thigh. Initial treatment for both sprains and strains includes rest, ice, compression and elevation.
Definitions of stress and strain. Nominal stress: the force on the object divided by the original area. True stress: the force on the object divided by the actual area. E.g., when necking occurs the true stress is the force applied divided by the area of the neck. The unit for stress is Nm-2, or Pa. Nominal strain: change in dimension / original dimension. This is also known as the engineering strain, and is strictly only true for very small displacements.