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