I was removing the mathematics from energy being potential to do work and work = force x distance. Granted, it's a very loose definition, but it does directly answer the question posed in the OP.
All the other forms of energy are (or rather, can be) measured by assessing their capacity to...
Is it? If it is, that's a mistake. I've never seen a Joule-meter (although someone may have
contrived one by measuring multiple contributing factors).
I like Richard Feynman's statement on energy:
My personal definition of energy is: The actual movement or potential to generate movement...