the word "prokaryote" refers to a specific structure that prokaryotes do NOT have that eukaryotes DO. "Eu" means "new/true", while "pro" means "before" andthe structure these names refer to is the nucleus. Prokaryotic organisms to not have their DNA enclosed within a nuclear membrane, while eukaryotes do. If you have ever gotten to look at samples of pro- and eukaryotes under a microscope you will have seen the nucleus of a eukaryotic cell, whereas the DNA of a prokaryotic cell is loose in the cytoplasm.