On another thread, we were talking about words that are both common everyday English words and technical terms. Sometimes, such as with parts of the body, the words mean exactly the same thing.
This thread is for words that don't.
Stress, Strain, and Pressue: In common every day English, these three words mean pretty much the same thing. As engineering terms, however, they don't.
Mathematically, stress and pressure are defined identically -- force divided by area. Generally, the term pressure is used when it's something else applying the force (water pressure, atmospheric pressure, the pressure that Hulk's footsteps place on the asphalt, etc.), otherwise the term stress is used, such as the stress applied to the wings of an airplane.
Strain is something completely different. When you pull on a metal rod, it will stretch a little bit. That stretch is called strain. It is calculated by dividing the change in length by the total length.
It is worth noting that within the elastic range, strain and stress are proportional (double the stress and you'll double the strain), so while they've very different things, they're closely tied to each other.
