A commodity is some good for which there's demand, but which is supplied without qualitative differentiation across a market. It is a product that's the same no matter who produces it, such as petroleum, notebook paper, or milk. In other words, copper is copper. The price of copper is universal, and fluctuates daily based on global supply and demand. Stereo systems, on the other hand, have many levels of quality. And, the better a stereo is [perceivedto be], the more it'll cost. One of the cha… (More on Commodity)