Darwin is much further from BSD than Android is from mainline Linux, and the Android/Linux distinction is entirely sufficient to call them different operating s

Darwin is much further from BSD than Android is from mainline Linux, and the Android/Linux distinction is entirely sufficient to call them different operating systems. I think you can accurately say that there are either two or five distinct operating systems in wide consumer use at the moment: Windows and Unix, or Windows, macOS, iOS, Android and Linux.