Just about any bicycle, that can be ridden, can be a commuter bike; it's just some are easier and more comfortable to ride. I rode a MTB(with slicks) a few years, when I got dusted by some older woman on a old hybrid (with a horribly squeaky chain) and a guy on a chopper style bicycle; I knew it was time for change on what I rode. My current hybrid is several MPH faster than the MTB, and uses less pedal effort, even at the higher speeds. The hybrid is much more enjoyable to ride, and greatly increased the number of my riding miles