pandemic?

So what exactly is this word pandemic, I've heard of epidemic, which is the introduction of the proliferation of a disease that spreads through a species, human (from wikipedia... for animals it's an epizootic), beyond what scientists expected or beyond what can be controlled or contained at the time that it spreads. But an epidemic is usually confined to a certain locality perhaps to a nation or a city or a building or a group of people. But nowadays you hear about a pandemic, in particular the Avian Flu (H5N1) which is now a disease that has spread worldwide outside the scope of a locality or a small group, it spreads between species through mutation. So pandemic essentially means that there is widespread continental or global infestation outside the scope of a locality or region.