What is a Curry?

Before I try to define that word, let me create an image for you from my college days in India, when I was pursuing a degree in chemistry. As I busied myself in the laboratory, I happened to knock a mercury thermometer onto the tile floor. Tiny pieces of glass and droplets of liquid mercury dispersed, and I tried to pick up the pieces. The glass was easy, but not the mercury. The shining, silvery liquid was elusive (not to mention dangerous) and defied containment and form (we had no mercury spill kits back then). It moved freely with even the slightest nudge and affected everything it touched. Which brings me back to the task at hand: Defining curry is like trying to grasp liquid mercury and gather it into a neat pile.