This is a semantics debate, but it kind of is an emulator. Instead of emulating a CPU, it emulates the Windows API. That's obviously a major difference: One is

This is a semantics debate, but it kind of is an emulator. Instead of emulating a CPU, it emulates the Windows API. That's obviously a major difference: One is inherently slower, while the other is inherently more complicated. WINE originally stood for "Windows Emulator", but for trademark reasons it was changed to "Wine Is Not An Emulator". That's giving you some mixed messages now, isn't it? [edit] I just checked Wikipedia, and that's not true -- the name wasn't changed due to a trademark problem, it was changed due to a genuine confusion about what the term "emulator" meant.